Im running a C6 but am seriously looking into a E4od or 4R100 swap. I live in a rain forest besides living on top of a hill. Im thinking E40d with 5:38 gears is the ticket.
I can get up and down my property and tow my equipment to and from auction.
I am trying to make this my "forever" truck and swapping in either a E4od or 4R100 would be like four new truck payments, so it pencils out. I am keeping all the receipts incase the truck gets stolen I can prove to the insurance company it's not just a raggedy old farm truck.

 

Those are electronic shift and will take some modification to put one in. You can do a ZF5 swap easier, but it is a standard.

 

The zf is a nice transmission. I have one in my bronco. Plenty of gear on the top and the bottom.

 

I have only ever seen 1345 in 1/2 tons. that should tell you something right there

 

Looks like the 1345 was used in F250's and 350's in 1981 and on: Transfer Cases - Gary's Garagemahal

 

The 1345 is older than the 1356, but used for comparable vehicle applications. My 86 F350 diesel came with the 1345. The 1356 is supposedly stronger, mostly on account of its magnesium main case vs. aluminum used on the 1345. Both are very strong transfer cases, both have positive pressure oil pumps.

 

NP208 is factory in the earlier trucks and is very weak. I've gone through well over a dozen over the years. 1345 I would not run, not sure if it's any stronger than a 208. 1356 is stronger than a 208 and bolts in. Shift linkage is a bit different but shouldn't be difficult to adapt to early shifter location or swap in a later shifter and cut a hole in the floor.

The 4407 or similar newer cases would be the better way to go if you want a married chain driven case that bolts on to the trans. They are slip yoke only I think so you'll need some minor driveshaft modification. The big thing that keeps me form running one is no speedometer drive. You'd need to figure something out or run an electronic speedometer using a later Sterling with an ABS tone ring.

NP205 is the strongest factory case but is not a direct bolt in swap. It is cast iron and heavy. At minimum it will need a torque arm/brace to the left frame rail. If mounting to an aluminum trans (ZF5 or C6) you'll probably want to make a full crossmember for it. Trans crossmember will also need to be modified or made new to clear the driveshaft which will be closer to the trans and lower.

I have a 208 in both trucks currently but have a married 205 and a fixed yoke manual shift 1356. Not sure which I'll run.

 

The 1345 came in Broncos and F250/350's, it is considerably stronger than a 208. Stock it has a wider chain than the 1356, and it has a deeper low range. Apparently the stock width chain is no longer available however. I've yet to take one of mine apart, and I have been abusing the one in my wheeling rig with 425 HP and 44's since 09.

The 4407 is fixed yoke with a flange, not slip yoke. It is very easy to identify just on sheer size. Compared to a 1356 it is massive.