for hacking off the cat, and loosing the AC i think you might get more like 20hp, not 40. a set of vortech heads and SDPC vortec/tpi base plate will net you 45hp i dont reccomend hacking off the cat. a high flow aftermarket unit is a better choice. headers, are a pain in the butt, but worth the price of admission. look at suspensino upgrades, swaybars, trailing arms, control arms, polyurithane bushings, springs, shocks, torque arm, torsen rear with gears, a transkit from B&M with a corvette 1st to 2nd servo, youd be amazed. the suspension mods are worth half a second in the quarter mile. aside from that, chips so long as its from someone you can do research on, you should be ok. someone that has a website, or a catalog or brosure they can send you. dont buy from someone you know nothing about. also look into holley stelthram intake, lingenfelter designed accel intake, 58mm throttle bodies, airfoils, cams. oh yeah, cams man, aint no better hp per dollar investment for a small block chevy like cams
i reccomend comp cams xtream energy line.