If your already at 200hp then you should be happy. Get you a set of gears and then you wont be bothered by anymore engine upgrades cause youll be roasting the tires off your gmc. Get you a good free flowing exhaust system and your in the money.
I have a mild 305 with edelbrock performance cam(rv cam)and matching lifters, stock 601 heads, headers, true dual exhaust, 700r tranny, 342 gears. and im happy. Last dynoed at 240hp/230tq.