texasinliner, when I was looking for brackets for a power steering pump, I discovered that even on the non-integrated head Chevys there are differences in the brackets. I swiped brackets from a van with a 6, but it located the power steering pump out a bit far (the alternator was fine).
I suspect there may only be two types. The difference was the width of the space between the two pulley grooves on the balancer. Some (like my 250) have next to no space, while others (like the van) have at least a 1/4".
Greg