That "reduced" diameter spit hole with the durabonds is "another" issue regarding the same set. I'm impressed you are catching all this detail! Good work!
In fact, one of our members here, "pineneedle", and I first became acquainted over this matter...and he knocked in two sets of bearings. John ended up manually "working" the spit holes back to the oem dimension using a die grinder/dremel. I know I've got pics of john's cam bearing install somewhere on the hd but can't find 'em! Maybe he'll see this thread and describe his workaround.
Buddydave tells me it was standard practice back in the factory branch when they rebuilt these engines (normally in batches of 10 units at one time), that they didn't spend too much time in cam bearing alignment. Got 'em "close" and then ran the proper diameter "aircraft" drill (12" shank with very short helix) through the ports to line up the spit holes after the bearings were in place. Then used a "de-burring" tool (hand held kinda like a paring knife onna swivel handle) to cut a small chamfer on the babbit surface of the drill bit left a rough edge. That way, spit hole alignment was not an issue as each bearing was actually matched to the block.
You are correct about making dam shore the cam bearings in your motor are right! The entire life of these engines is dependent upon that and a clean water jacket! So if it takes hand work to make the match up, spend the time to do it. Then we'll continue to ream on durabond until they respond!
Take a buncha pics of your cam bearing deal, nice detail and well focused. We need documentation of an actual durabond install regarding this issue so we can get this matter resolved. Right now though, the durabond bearings are on my "ignore" list.