I would get a pre-1974 German car if I don't have one already. I'd keep the body stock...
change the wheels to EMPI style wheels
replace the fronts with disc brakes from a Super Beetle or get the replacement kits
Rebuild the engine, put in a modern alternator to replace the generator, get new Weber carbs, or better yet if you have the funds, get 2.0 or 2.2L rebuilt engines from the US
Rebuild the tranny if necessary
Check and fix the electricals, rewire, replace the fuses with the modern type
Get all accessories working - wipers, washers, gauges
Drain and clean fuel tank
Body repair and repaint
Replace rubber seals, running board, moldings, chromes, emblems, etc. if necessary
Reupholster
Decent stereo
Air conditioning