Originally Posted by Epstein

Among SR brackets, there are 2. The redtop and blacktop. S13 Redtop has a redtop bracket. S13 Blacktop has a blacktop bracket. Late S13 with the screwy compressor has the same blacktop bracket. The S14SR bracket is the blacktop as well. These are all interchangeable on the block side. I'm running a redtop bracket on my S14 SR.

I've seen an S13KA compressor on a redtop bracket; the so-called 2-bolt solution. The 2 bolts that don't line up are varying degrees of not-close, IIRC. The S14KA compressor against this redtop bracket is VERY close. I didn't try it, but it looks like a dead bolt on with perfect hole alignment. This "bolt on" ignores the different pulleys that make it actually not work.

I've never seen anything bolt on to a blacktop bracket that wasn't a blacktop compressor.