Your problem is the mount, not the alternator. Had to get creative with my repro SCJ mounts to even get it on the outer run of the pulleys I had (2 sheave). Now that I went to a smaller single sheave, seemed to line up perfectly fine as the mounts were designed to work!
I would recommend SCJ alt mounts! Bought my polished S/S ones for around a buck or so from this company that sells them on occassion on Ebay (I just emailed them to buy them, C.R.A.P. is their company name as I recall, I'll look and see if I saved the receipt in the morning before I head out to the water).
Shouldn't make a ton of difference on the alt I wouldn't think. They all mount basically the same as far as I have seen.
Ray