It depends on how much work you want to do to get it in and running, and how much you want to spend. Do you want fuel injection or just a good 350 for a carb? If you want an easy swap, look for a 350 TPI(RPO code of L98) from a Camaro/Firebird or from a mid-late 80's Vette, even without the TPI setup. The L98's had 225 -245 HP stock. They have roller cams from the factory. Plus they had a compression ratio of about 10:1 with 60cc heads. With 64cc heads, you would have 9.5+:1. Throw in a cam, a carb intake, and a decent exhaust and 300Hp is not far off. If you keep the TPI, you can make some good power and still get decent gas mileage. LT-1's and LS-1's are not cheap to work on or install.