97 suburban tensioner problem

I changed a clattering tensioner a month or so back with a Gates 38103. no more rattle, but now that I look at it a little closer, I see that the tensioner pulley is about 1/4" forward from the alternator pulley, and all the other pulleys, for that matter. I got another tensioner with the idea that I may have had a mis-labeled replacement, but it appears to be the same. unfortunately, I discarded the original, so don't have that for comparison. I have tried various configurations to try to seat it to where the pulleys are in line, to no avail. anyone have any alignment ideas before I trash the belt?