Bassically you can go as crazy as you want, if you have the cash. For a reasonable price, expect no more than 200 hp. You could always just get a LC supercharger for it, im sure that would wake it up.
As for what i did, i almost consider a Cam to be manditory, it sure seemed to wake mine up, although i rebuilt the carb, put a better ignition on it (robbed coil from a supra, new cap, 9mm wires, and NGK plugs), and went to a 2.25" exhaust at the same time. I was happy with that, it sure moved compared to my 6.2 diesel K5.