Cam bearing issue

How would they size the cam bearings? That's new to me.

OP I saw in your add it's a magnum block and an LA cam. technically there are 2 different part numbers for cam bearings between an la and a magnum block. The magnum cam bearings are slightly thinner. They should be the same ID (from what I have read online) but I'm wondering if this could be a possible cause for your issue...