The bearings must be strong enough not to flex or deform when the dynamic stress work on them. They have to keep their shape during extreme loads and temperature changes.
The oilfilm between the rotating part and the bearing transfer the forces from piston/rod/crankshaft to the bearing. The more power in the engine, the stronger and accurate the bearings must be. They are not alowed to deform.
These sites explains it all in a good and easy to understand way.
Hydrodynamic Bearings, by EPI Inc.
http://www.mae.ncsu.edu/eischen/cour...ringDesign.pdf
I would not judge a bearing producer if a store did not supply the correct size of bearings to a certain engine. I would double check the dimensions of the engine parts and get the correct size bearings according to that.
I have built enough of high powered engines to know the needs and demands.
In my latest very powerful ca18det I use ACL and they are spot on.