318 (275 Hp)

Stick a better cam in, and if the intake is stock, you could do better with a small port intake. That one will have 340/360 ports. Also, Thermoquads only come in 800 and 850 cfm versions. But are great on a mild build. I'd go XE268 and stick an Edelbrock 650 on it for ease of tuning. Also, headers will make a big improvement over any 318 type manifolds in power and weight. The 340 type exh manifolds prior to '72 would also be good, but more $$. Lots more.