There are companies that make aftermarket replacement condensors that bolt right in. There are cross-flows and there are tubed replacements with more, thinner tubes. Either do a much better job of heat exchange than the originals. The important thing is that the volume of the condensor matches the volume of the expansion/exchanger under the dash. The pump is looking for balanced volumes to operate properly.
And, do yourself a favor. Get rid of the York compressor and get a Sanden 508. The rotary compressor is smaller, quieter, vibrates a hell of a lot less, and doesn't drag down as much horsepower. I used a tube condensor, kept the under bumper unit, and have R-12 in a Sanden. I'm getting 38 degrees F out the vents.
Ray
'68 280SL 4-spd Coupe