I ran into a similar issue with a comp solid roller in my buddies 440 based 496 stroker. The engine had been together before previously with a 292/.509 purpleshaft installed with no cam fitment issues. We decided to freshen it up and and upgrade to a roller cam from Comp. After driving in a new set of cam bearings, the new comp roller wouldnt begin to go into the block. I then grabbed the old purple shaft and it went in just like it should and turned freely. Next I grabbed my new in the box Comp solid roller for my hemi project and tried to slide it into the 440 to see if it would fit. To my disbelief, it went right in and, turned freely. I then got the micrometer out and started measuring the journals. They were the same. So then I called Comp and told them what was happening. At first they tried telling me the camshaft bore was off in my block. After explaning that I had tried another of thier own new cams and it fit well they agreed to get me another cam. Got the new cam back and all was good.