Help with my build please. 70 C10 Short Stepper.

[bzblaine]

Intro
1st of all, I'm brand new to the forum. Hello all! Blaine here from San Antonio Texas. Just bought me a 70 C10 Short Stepper. I love it. Its always been a dream of mine to have one and my dream has come true. Granted, I don't know a ton about building a vehicle, I know enough to get by. I've been searching the forums for weeks learning stuff about my new truck. I have some question for those who don't mind helping me.
Truck Info
I have already purchased a 468 BBC and a built Turbo 400 trans. The truck was originally a V6. My buddy is building the engine for me. We are working on a budget. A tight one. But, he says he can get that motor into the 550 - 600 HP range. He has done it several times in the past, So, I trust him. This is going to be very fun Daily Driver. I'm aware of the terrible gas mileage, and I don't mind as I didn't get it for the mileage.
Questions
I'm assuming im going to need upgraded suspension and rear end. Being as we are on a tight budget, I would like to know what rear end would be easiest to swap into here and be sufficient for the power we will putting into it. Any suggestions for suspension? Diff? Posi, front end?? I am looking for the cheapest, easiest, and durable solution. Preferably a swap from a donor vehicle currently possessing the qualities I need. Any information would help a lot. Also, as a bonus, Im 6'4 320 LBS. I would like a split bench seat, with center arm rest/console. I need one with a thin back to allow for the most room possible. Again, Any info would be greatly appreciated. Sorry for the lengthy post.