A few years back, the Volvo dealership converted the a/c in my wife's '91 740 to R134a. It has done fairly well from a cooling standpoint, but the compressor died. I have a new compressor and bought the newer style manifold/gages, but now the high side connection is wrong (same style as the old R12) and of course the new manifold gage set will not attach to my vacuum pump. I was always very successful with a/c work in the days of R12, so have the basic skills. What adapters are available to meet my needs?

The appropriate adapters should be available where you buy your refrigerant.
Make certain you replace all of the oil that came with the new compressor. I won't work with R-134a.

Thanks, the comp came with the correct R134a oil