I think you’re going to find there are only a few sizes of roller cam bearings available.
Usually something like 50, 55, 60mm.

Obviously the cam bores need to be bored to fit, and plan on needing a cam with the cam journals sized to go with the bearing diameter used.
Check with your favorite cam supplier for availability.

If you’re currently oiling the top end with the factory style “thru-the-cam” oiling, you’ll need to sort that out, since that option will go away.