Just don't make too big a deal out of it. Buy the one for the same application as the alternator and it won't matter what the part number is, or isn't indicating.

Wiring is not a big deal on any of them, as long as you don't mind wiring!
As far as idle power, most newer designs are better in at least some ways. The exception was the sometimes-infamous 2G from Ford, where the power output was pretty decent if I remember, but it had other issues. It wasn't so much that the performance was not there, it was that the usual safety net was not designed into it.
Which I believe is what resulted in Ford's newfound religion of overkilling the charge cable now. No manufacturer uses 6ga and even 4ga battery cable sized charge wires without reason. And lawsuits are probably right up there at the top of the list for why spending more money now seems a good investment.
Interesting about that aspect, is that GM automobile owners often perform what is known as the "Big Three" modification. That's where they, by necessity I might add, up-size not only the two main battery cables, but in particular the undersized charge cable. Big electrical performance gains are the goal, and the Big Three is how you get a good jump on it.

Ford has already done that on modern 3G and newer charging systems, by running a minimum of 6ga battery cable. Whereas our older vehicles probably had 10ga instead. Just barely enough for the 55amp alternators of the day.

Never heard of that being a necessary evil of up-sizing an alternator, but I don't know everything about what is needed with older trucks.
For example, is your truck's ammeter a shunted type, a direct reading type, or an inductive type instrument? This can make a HUGE difference in how you approach the wiring.
But for general purposes, the generic answer is to simply bypass the ammeter and wire the alternator directly to the battery, if it is not already.
In the later seventies models at least, the charge wire is in fact wired directly to the battery (via the starter relay) and the ammeter is a shunted type that only samples the current and creates a reading on the gauge.
In this case you don't have to worry too much about wiring under the dash.

If you have a direct feed-through type, or an inductive loop type ammeter, you still don't have to change the wiring behind the dash. But you do have to change the charge wire under the hood.

I know there have been diagrams posted of your vintage truck, but I never bookmark them it seems, to grab a peek when I need to.
If you have not been behind the dash, I'm sure some of the others following this discussion can inform us as to what type of ammeter you have in yours.

Paul

 

IN fact if someone has a handy link to the general area of Fordification that has the wiring diagrams members here are always posting, that would be great. I have the '72 lighting diagrams saved, but the alternator section only shows the standard wiring and not that for an ammeter.

Thanks

Paul

 

You beat me to it - the charging cable.
Upgrading to a 100-amp unit, regardless of which model, means (to me) that wire needs to be upgraded. The stock Ford 3g has the 6-gauge cable, and also an inline circuit breaker. (aka the MegaFuse)
I would not skip this step if going to a high-amp alternator. Don't try running 100 amps through a crusty 50-year-old wire that was only meant to handle 65 amps to begin with.

So again...it may be easier to stick with what you've got, or at least something in that amp range.

 

1TonBasecamp -- Well Paul, it's not the wiring itself that is the problem, It's more where the harness are located. I can't get down on the cab floor on my back & work under the dash. I am good with stuff in the engine compartment. Takes young dudes to that type of truck wiring service.

I did pull up a "you tube" on a 3G from alternatorparts.com that they have a harness that plugs into two places on a 3G and has two other wires to connect. All you need from the old original regulator is the keyed wire from ignition.

What is a good price for a 3G from wreaking yard for the alternator only? Thanks Tom

 

Not sure current pricing. Around here the Pick-n-Pulls are kind of expensive, but still likely charge about 30-40 bucks or so. And probably have a special for 20 bucks now and then too, but not sure.
And you could take the old connector from the junkyard alternator, and may even be able to salvage some of the nice 4 or 6 gauge Black w/orange stripe charge cable while you're at it.
But that's for the 3G. You were not talking about a 100a anymore though, as you had settled on a 70a model which may not require upgrading the charge wire.
But that is exactly why I was curious which wiring scheme your truck used. As I mentioned, at least the later Ford trucks wired their alternator directly to the starter relay, which means that the charge cable is probably the standard 10ga type and just a short run of maybe 12 to 18 inches or less. More than enough for a 70a model if it's still in good shape (being in good shape is always the key with these old rigs!)

If you opt for the 3G after all however, you will make/buy a new larger charge wire and Mega-Fuse (or Midi-Fuse) with holder anyway, like rustywheel mentioned.
Would be similar to the #6025 listed on this page: https://www.wildhorses4x4.com/category/Bronco_Starters (which looks to be on a Black Friday special anyway)!
Unfortunately I don't know if it's the proper length for your truck or not. You could probably make it work easily, but if you want to route the cables a certain way and mount the fuse holder in a particular location, you'd want to measure the wire lengths and we could probably make one for you. Would not qualify for the special in that case I don't think, but if the lengths are not much different from the existing ones, you could just use this one and take advantage of the special.

Still lots of choices in direction to go yet.

Paul

 

My local pick-n-pull charges $25 for a alternator.
A remanufactured 63-amp Delco 10si is $40 at Autozone, with a 1-year warranty.

 

1TonBasecamp -- I do not have a working original amp in my dash, I use a volt meter mounted under the dash. I have a 8 gauge wire running from my 65 amp alternator to the + side of the starter solenoid. This would be fine for a large case 70 amp but if I went to a 3G 130 amp I would go to a 6 gauge with a 150 mega fuse.

rustywheel68 -- Thanks for the numbers.

 

Here is a good primer on converting to a Ford 3G alternator:
https://www.hotrod.com/articles/inst...r-older-fords/

 

RichS2659 -- Thanks for the great site on a 3G modification. I am still looking at a new Tuff Stuff 7068 1 wire 100 amp unit at $90, it has a low idle cut in on it's internal regulator that will charge greet at low RPM like I do in my truck around town. either way I go I will upgrade my charge + wiring to a 4 or 6 grade wire & install mega fuse in line. I think for the little, light driving I do I am leaning towards the 1 wire 100 amp along with it being a new unit set up for my v belt. I have time as my 65 amp 1G is still working fine.