No 235 engine (car or truck) had a full-flow oil filter from the factory. A full-pressure 235 would only be possible if someone converted the block. The 1958-1963 261s were the only full-flow oil filters in Chevrolet or GMC engines of that era.
How many RPMs are you turning the drill/pump? I had to turn mine fairly fast to get oil up to the rocker arms.
(Also, I have to ask: did you take the cam gear off the distributor-shaft that you are using to turn the pump? If you have removed the gear, ignore this question - no need to reply.)
