1.06 T-bars
Stock RR/GTX rear springs
QA1 adjustable shocks
AndyF Brembo disk kit
AndyF or DocterDiff rear disk kit
Appropiate aluminum master per AndyF
Firm Feel tubular upper control arms
rubber LCA bushings
gusseted reinforced K-member- Firm Feel does this.
1 1/8 Firm Feel front sway bar
3/4 Firm Feel rear sway bar
US Car Tool subframe connectors
275/40/18 front tires
Firm Feel power steering
stock ratio pitman
1/16 toe in, 4 deg postive caster, 1.5 deg negative camber

XV strut tower brace would be great too, but I would hold off until you got your turbo plumbing setup. Also XV raditor support and inner fender brace will reduce cowl rattles and flex.

Will not feel like any old 4000 stock 71 B-body.
Will be super responsive at 30 mph and at 80 mph.
Will have great braking

That's keeping it simple, pretty stock looking, and some change still in you back pocket.

Since you are planning on a twin turbo 508 big block with all that plumbing the extra room would be a big plus and trick look of an Alterkion would be a "fit" for your project. I've seen them powdercoated in hammertone black/grey that looked real cool, gives it some contrast, but wasn't gawdy.

Alterkion would give you some great flexibilty with room and fitment. It has the level brakes as AndyF kits and good adjustable QA1 shocks as listed above. Just pick some agressive coil springs.