Ringed engines are not ABC. OS makes the following in the 40-50 size range of 2 strokes:
40 LA BUSHED
46 LA BUSHED
40 FX BALL BEARING
46 AX BALL BEARING
50 SX RINGED BALL BEARING
I prefer ball bearings, other than that the listed motors are fine. I have read stories of the LA's having problems at times, opinions- there are a million of them. Some of these are ABC and some are ABN, just a different plating on the cylinder wall. Either is fine. Need to determine your application and select the engine that best fits it and possible future use. Do not overpower my to large of a degree, speed is not everything. It is a lot, but not everything.
Bruce[