Hum, starting from scratch, eh? Well, take care of all the rust, make sure the frame is strong, then;
build up a 351 Cleveland
Find yourself a T5 or similarly tough 5-speed manual to put behind it
Get a posi 9" center section and some 31 spline axles
Get all new springs (LTD wagon springs from a junkyard work good for the back, the HD springs you can get from NAPA for the front)
If it doesn't have one already, get the Saginaw steering gear and pump!!!
I've heard tell that, with just a little bracket fab, you can use another front sway bar in the back to increase roll resistance. Haven't done it, though.
Get 15"x8" wheels, and invest in some P255 60 R15 tires! They fit without any mods, and you'll love 'em, trust me. (and they look bad-ass)
Do what you can to stiffen up the frame; roll bar, hard body bushings, cross bracing, whatever you can come up with.
If it doesn't have them, get a sport dash (with all the gauges) and the console from a console-shift car! And the bucket seats too, by neccesity...
Just a thought; plenty of room in that engine bay for turbos and intercoolers... ::Grins::
Just my thoughts if I were building a car from nothing. It really depends on what you are looking for your end result to be, and how much you want to invest.
Happy motoring!
Mike