I know the subject has been discussed but i don t have a clear view so anyone who really has an opinion please contribute.

The R&O if i understand well prefers the "thrust" bearing as it absorbs better the force of the clutch when dissengages.  some are called angular thrust bearings but then the suitability for us depends on the angle of the "angular" right?

Others prefer the deep groove bearings because of the ability for some thrust applied and because it has more rigidity on the countershaft.

My 1931 is being redone now and i used to have a lot of vibration after 35-40 MPH , perhaps the bearing was at fault? it was a SKF 6207 and had noticeable wear inside.