We use sweatshirt/hoodie material for sub/speaker enclosures, a little thicker than a tshirt and forms a little smoother over corners/edges. Like where your headed with this project though.
I run 4.10s and 35s with a T350 & NP205....screams at highway speed, around 2600-2700 rpm. I can spin the tires easily on gravel, even in 4wd, with a basic unadulterated 350 4bbl.
The older 5.3s are great for swaps as they are cable operated throttle bodys. The 243 heads are the ones to look for. The 4.8 pistons do fit the 5.3, they use them in the H.O. 5.3(L33), it ups your compression to 11:1 Iirc.
It came with a D44 up front and a 12 bolt in the back, I had a '74. Unless you swap to manual lockouts or have a manual(or got really lucky) you'll always be running in 4wd as they came with a NP203 transfer case.
I use it every other oil change in the crank case. I tried it in the fuel(on my '76)and ended up needing to replace fuel filter with all the nasty stuff it dislodged . Run it every 6 months thru my '01s fuel system, and use it in my motorcycle and quad.
I'm with Bucket. I do suggest taking them apart and servicing them. I just did that to mine today and found cracks in the one housing and a broken turn knob on other side. Hubs are often overlooked when it comes to scheduled maintenance.
I put ammeter onto battery with a buddy and went circuit by circuit removing them until drain ceased. Turned out to be my cb radio, amp and p.a speaker. Somehow it was left on and was firing up the amp to the p.a.