[How do I convert the half shafts to CV joints, Brake and tire ??]

I have a 76 with the same setup. R200 with 3.54 ratio. Silvermine motors makes the adapter for 180 bucks. They also have a complete kit with axles. The CV axles I purchased was from rock auto. 84-89 Nissan 300zx turbo, Z31. Work great. Just tig weld the adapter to the companion flange. I paid a hotrod shop to do the perfect welds and I still have about 400 bucks into that part of the project. Good luck to what ever you decide. 

[4.8 swaps?]

Yes I did a 4.8. After installing a new cam, a litle head work, and some headers, It was putting out a little over 320 horse power. I used the mounting kit from johns cars, and headers, air filter, radiator from JTR. I went this way because you get just as much power out of the 4.8 as the LS1 for way cheaper, and it runs on regular unleaded instead of premium. And best of all, I get between 28 to 30 miles per gallon. Good Luck