I havnt bought the alternator yet. I have been looking at measurements on some of the chrome items on offer. Was going to make a up a card board mock up and see what size will fit before buying.
Not very clear, but you can sort of see the issue in this pic.
I originally wanted to put it high on the passenger side so that the belt could wrap over the tensioner and under the water pump. I think I will have to put another idler on up high on the passenger side and mount it below like you have. The tensioner i have on there now is manually adjustable
CBM-10712 LS1 LS2 LS3 billet belt tensioner manual Camaro GTO NEW f body LS6 LS7 | eBay its a nice bit of kit and means i dont need to have an adjustable bracket for the alternator.