My first R block with 48 degree used standard cam bearings. One R3 used a 2" babbit. We bore the cam tunnel to take 50mm roller bearings. The other R3 was 60mm. These were all 48 degree blocks.

There is nothing about race blocks set in stone. Don't know why guys keep implying there is. Some part numbers are repeatable but many of the blocks are different depending on the date and mood of Mopar.

Leon