This 77 is full time 4X4, with the divorced transfer case. What will I need to do to make it part time? I do have a set of lock outs for it. My other 77 is part time and the drive shafts look different. Why is that?

 

For mods try this driveline forum.

 

Chances are that one is a NP 203 (part time), and the other is a full time unit ( NP 205 ). This is why the drivelines are different.
If you just install the locking hubs, and attempt to move in anything other than HILOC, or LOLOC, the truck will not move. The full time cases have a differential inside of the case that allows the front and rear axles to turn at different speeds. This allows the truck to move on pavement without that "chunking" that occurs with part time units.
A part time kit requires the case diferential section be removed, and modified to run in loc mode all of the time. Now when locking hubs are installed, and placed in the free mode, the truck will still get power to the rear shaft, and you will go foward.
The other big differences between the cases are the internal components. The 205 has a gear to gear configuration, and the 203 has a chain. For reliability, and strength reasons, the 205 has an advantage, plus it is already a part time unit. Since you already have all of the stuff from the other truck, why not install the better case from the donor truck, and all of the related components? You already have all of the driveshafts (3), it sounds like. I feel this would be a better deal for you. Most guys spend quite a bit of money to get themselves exactly where you are at. It is a pretty easy swap. The only tough part would be if the donor truck is a 77.5 and not a 77. The 77.5 will have a married t-case.
You also have the makings for a "doubler" set up. This uses both the 203, and the 205 case in series to double the overall crawl ratio. Maybe not a good idea for DD aplications, but don't give away your 203 if you swap it for the 205. It still has pretty good value.

 

Thanks for the info 75F350. My kid and I both have 77 Hi-Boys, part time 4X4. I got this 77 Hi-Boy for the cab. Mine is bad under the incab gas tank. But this truck is to good to part out, all it needs is brakes and a bed. I will just leave it full time 4X4. I did not know the cases were different. Thanks

 

They may not be, but you had mentioned that the shafts were different. This tells me that one is possibly a 205. There is an identification tag on both of them, probably with plenty of years of grease on em. You can easily id the 203, by the big ouptut section on the rear. This is where that differential is. Couple of other ways too. Snowplow guys love the full time 203, cuz they can run on the pavement without binding up.
You can find part time kits for as little as $100.00, and they are easy to install. You get what you pay for however, so do a l;ittle research before jumping into a real cheap kit.
Good Luck with those trucks. Hope the info helped.