It depends on what you want. I have an 85 with the 305/200c combo. No problems ang good mpg at 133k miles. If mine ever needs work, I will probably go with a 350, mild cam, good heads, possibly headers and either a turbo 350 with my stock 2.41 rear gear or swap gears and go with a 700R4. If I were to have access to late model stuff at a good price (like I was connected at a dealership, natch) I'd seriously consider LS power and maybe a six speed. (My 05 GTO is such an amazing combination of docile driveability, fuel economy, and expletive-producing power.) Even the 5.3 with 320 hp is a big step up. Wanna get wicked? Put a ZO6 LS 7 in it. Upgrade the to the trans on your choice, get a Grand National 8.5 rear, do a brake upgrade, and off you go. Patrick