I converted my car to r134 and it cools great when moving but, in stop and go traffic is not as cool. However, I don't remember too much of a difference with R12. As you know, the 124's A/C is not its greatest asset...
I just helped Neumann replace his evaporator, I think you already got in touch with him, but his newer system already has r134 from the factory. He has a 94 E320.
BTW, when are you moving to the area? Did everything work out for you?
See you!

__________________
J.H.
'86 300E