If all other tune-up settings and, ignition parts) are good, the carburetors (as suggested by others above) would be my guess.
Forgive my needing to ask (and, forgive my stupid questions), Ron, but what carburetors do you have on the 1954 235 engine (looks like it was overhauled in 2007)?
"Offenhauser intake and Fenton headers."
Have you measured compression?
