I'll ask you guys, there are more of ya. 68, F750, stock alternator & regulator to a 1 wire alternator - stock gauge has - &+ is this volts or amp ? Do I need to run any wires from the old disconnected regulator the dash gauge ? Any other wires ? Any comments using a GM 1 wire ?
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Sounds like you have an ammeter instead of a battery charge indicator lamp. So no, you do not re-use any of the associated wires and would benefit from converting to, or at least adding a separate volt-meter.
If utilizing a true 1-wire (self exciting) alternator, you only need a charge cable running from the BAT terminal on the back of the alternator, over to the battery positive. Usually to the battery side stud of the starter relay/solenoid. Rather than directly to the battery terminal itself.
The size/gauge of the new wire you use for charging duties depends on whether or not you upgrade the output rating as well. A stock one (even for an F750?) would have been from between 45 to 55 amps usually. Maybe there were higher output versions for your larger truck, but if the small case variety, probably not. Is yours a small-case 1G alternator, or a large-case version?

You should not need any further wires in a 1-wire setup. Other than adding one for an indicator lamp.
I'm not completely against using GM alternators, but I prefer the Ford 3G models myself. No real dedicated reasoning. Just that sometimes I like to keep Ford for Ford and GM for GM. However, the obvious benefits of a typical GM alternator are widespread availability and usually lower prices.
But the 3G is a good quality, tried and true unit. Available in two standard outputs (95 and 130 amps) and many up-rated outputs. Not as many as the GM models, but enough for most uses.

Got pics of your setup? I know that while most of this stuff should be the same between models, your larger chassis truck often has some subtle (but important) differences under the hood.

Good luck.

Paul

 

Smaller case. Do I have to run a light or volt meter ?

 

It’s an either/or situation. Or both!
I prefer a voltmeter to know a little more exactly what’s going on ahead of time. But a supplemental light to get your attention, in case you’re not watching your gauge is not a bad idea.
And probably why all modern cars that have a meter still have a warning light.

 

While updating the alternator, do you plan to go to a more powerful one?
I mean, that’s almost a given, since most one-wires are more powerful than the older ones were. But are you planning to go regular like something in the 72 to 80 amp range?
Or will you be going big with some thing in the 90 to 100+ range?

it also occurred to me that your 750 maybe has a different type of ammeter than the smaller trucks.
Back then some manufacturers were still using pass-through ammeters where the whole load was handled by the gauge.
Even though you won’t be using the old ammeter either way, a pass-through gauge that is directly wired to the charge circuit is a dangerous thing to have go wrong.
If it is of that type, you won’t be utilizing any of the old ammeter wires. And since I don’t have a diagram of how they are connected, you may end up having to remove, or at least to cut and safely cap off the original wires.
We just have to be careful about that because of possible integration it to the rest of the power circuits.

Maybe someone with direct experience with your type of gauge will know exactly what has to be done.