Best part of truck to start buildup...?

[67'ShortMonster]

What should i get done first...

1.) The frame.... Makes sense... working from the ground up.

2.) The body.... This is the part everyone sees anyways.

3.) Engine and drivetrain... you can't go anywhere without it.

4.) Don't worry about one specific thing. And just get it on the road for now...?

Just need to figure out what I should concentrate on first to get my project going in the right direction again.
On another note, I need to decide what to use as an engine. I took the one i was gonna use for my jeep.
My options i am considering are... the engine from a 1999 Trans-Am. Not sure what it is exactly... it was a convertble v-8 car is all i know. I can get it cheap because the car went off the road. My uncle towed it, and has been storing it for three years. No insurance when the guy crashed it. Rear end and tranny would also be available...
The other option i was thinking of was just a fuel injected 454 from a mid 90's truck.
Or... Maybe a TPI 350 on twin turbos... That would be cool huh.
I am %80 sure i want to go with a automatic for a tranny.

What does everyone think...? I need some guidance here.