G'day MF,
We'll really have to wait for one of our 'mowernalia' collectors to come up with the range brochures, or the Victa dial-type 'quick parts finders', for the years in question, to get the answer to this one.
For the full crank engines, as far as the 125 being a 'better engine', it was of course not as powerful as the 160, but it was more durable.
A 125 could usually have several replacement sets of piston rings before needing a rebore. The 160 bores tended to wear oval, so if the rings were gone, it would almost always need a rebore.
