Since this looks like a general A/C thread - I've been looking into W123 parallel flow condensers and see that some people have installed dual condensers. There's a 14"x23"x44mm double-thickness parallel flow condenser on AliExpress that looks appealing to me. I could have a local A/C shop make hardlines for it to connect to the stock W123 hoses. If I've measured it right, there would be roughly 1/2" between the condenser and radiator.

I added a W126 aux. fan plus manual override switch to my '80 240d to help stop-and-go A/C performance, which is somewhat passable (about 35 degree drop) but I want better. It might also be possible to install a higher volume interior fan from a different car too.