mmmm....sounds like they just gave you a quote for the likely cause and would then work it out on the day if you said yes.

That is a lot if it supply only, to give you an idea I had a new compressor fitted to my car recently, good brand $600 for the unit. A year ago I had a new correct BMW part for my 635 at it was just over a grand. Of course it plus,plus,plus after that for fitting, charging etc.

Interesting thought from the a/c shop. I assume then its probably not well cowled from the radiator back to the fan? The much shorter V8 leaves a lot of space there , and if its left open it doesnt help the air draw through the radiator.

You should touch base with rickxj6 up there, he sounds like he is having engine transplant thoughts as well in his XJ :-)

Good luck with getting things sorted and your project under way.