I have a 72 RB that Ive had for over 20 years. This block has major issues with the cam bearings...

First time I pulled a cam out of it, one of the bearings was spun. Had a guy come to my house and put a new bearing in. Tried to put the cam in and had to hammer the cam back in. Didnt know (or care) any better and fired her up. She turned over really slow till it lit. I guess the bearing clearanced itself pretty quickly. Never had another issue with that cam.

Rebuilt that motor a few years later. Sort of forgot about the cam bearing problem... Short block all assembled, try to put cam in block. No fittie. Buddy who was helpin me hammered the cam in and ran a bolt down in the front of the cam. Chucked the bolt in a drill, trying to spin the cam. Worked for a few minutes till the bolt broke in cam. Ended up making a ream with a factory MW cam he had lying around. Reamed all of the bearings and hoped for the best. Never had an issue and the bearings all looked good a few years down the road.

Same block 10 years later. I paid a machine shop to "correct" the block. Machinist told me he had the proper tooling to correct the block. Pick up block and machinist scrapped the bearings to fit the cam. Still no issues, so whatever..

78 RB block in my car at the moment had 2 tight bearings. Reamed them also. No issues with it.

400 block that is going together at the moment has one bearing .001 tight. Gonna hit the cam journal a .001 and call it good.