Gearhead's right.
A 235 will never get to 350 HP reliably. A 250 probably won't be very driveable if it did get to 350
real HP. A 292 or a GMC 302 would be your best bet.
Even with those engines it will take a
LOT of work and money to make 350HP, unless you are drag racing and go with nitrous or turbo or supercharger. Without those mods a 292 will never even come close to 350 HP.
I run a 292 now in a street driven (could be daily driven) 1966 chevy truck. It's bored .060 over and has a 500 cfm 4 barrel carb, long tube headers, HEI ignition, etc., and produces nowhere near 200HP. So you can imagine what magnitude of changes would be required to approach 300HP.
-magic mike-
