been thru this a few times. used to do the "bearing sizing" with an old cam but would rather not anymore. i think the issue is journal run-out or size on the camshaft. the only way to really know is check size and run-out on the new cam. the last one i did for myself was a little odd. i had 3 cams i could use for one engine and the first i tried wouldn't go in but the second fell in. i didn't want to cut the bearings so i just ran what fit. the bearings are soft and have a lot of conformabilities. checking the new and old camshafts journals and run-out will tell the story if cams or bearings are the issue.