350 hp with a 235 isn't going to happen, at least not for very long. 200hp is about the best you could hope for with a normally aspirated 235 on the street, and that's with ALOT of head work and other things that get real expensive, real quick. Not positive, but even with a 12 port head and a turbo, my guess would be that if you do hit the mark, the head gasket won't last long (even with o-rings) due to the lack of head bolts in key areas. Others may disagree. If you want a reliable 350 hp from a six, a turbocharged 292 would be my suggestion. Of course, that means swapping out everything from the bellhousing forward (if stick) tranny also (if auto). New motor mounts, radiator clearance???, hood clearance???..... $$$$$
