Yes, the 124 is a worse candidate for 12 to 134 conversion than is the 123 car due to a too small condensor. The good news is that the 124 cars were among some of the earliest to come from the factory with 134. As I recall I looked at a 91 that was factory 134, but it might have been a 92.

That said, here's my response to all these questions that you ask: None of that really matters unless you are deciding between two cars in the exact same CONDITION.

By FAR, the most important three criteria when selecting a used car are:

condition
Condition
CONDITION

With all the questions you asked, it's pretty much a wash. Just find a very nice, very well maintained example. That's more important than any of the other stuff. When you're buying a NEW car, then those are the kinds of things to consider, but not with a used car.

My $0.02,