Installing a/c help!

It's not the compressor you have to convert. You probably need a new expansion device, flush the thing out real good, and be sure to get ALL the old oil out of the system. 134 is certainly the way I'd go, this does not sound like a "concourse" resto.

I'd get ahold of some of the aftermarket air outfits, don't remember the names, "Classic Air" is one, here's another: http://www.oldairproducts.com/catalog/ and AMA has been around for years:

http://www.ackits.com/