One thing to remember is that the 305 is about the same rpm engine than the 235. Crankshaft balance is horrible. If you run the engine at sustained revs over 2,700 rpm you will end up with a rod through the block. I know from lots of experience working lumber yards in the late 60s to mid 70s.
And parts are hard to come by.
Besides the gobs of torque, they do have another advantage. You can usually get a running 305 out of a pickup for free.
