I have two Euro 123's, both not much more than parts cars. They both have aftermarket A/C with a Sanden compressor. The bracket bolts the Sanden solid in place and uses an idler belt tensioner as I recall. They don't hit the IP, but they are set up for one belt as I recall.

I was afraid that the bracket I referred to might mount the compressor to another bracket rather than adapt to the R4 mount points. Sorry if I sent anyone on a wild goose chase.