how would you guys built it?

If you have a strict budget, concentrate on teh importnat things... You need the V8 swap stuff and decent exhaust regardless of the hp goal. And... You ned a V-8 rear (8 3/4) for it... again, regardless of gear ratio. I had a ton of fun with a 2bbl 383 in a one legger 8 3/4 in a dart years ago. No, not a lightning bolt at first, but reliable and fun which is the best palce to start from. Lose the performance goals, and get it in and running reliably stock. Then move forward when you can with bolt ons and better gears/sure grip.