I've got a '77 RS. I've got a 120 Metzler ME880 on the rear, and it works great, no rubbing at all. I had it done at a shop, so I won't speak to how difficult it was to put back together. I currently have about 10K miles on my Metzlers, and they could go for awhile yet.
"By the way, you don't have to be sweaty and holding a basketball to enjoy a Gatorade. You could just be...a thirsty dude! Gatorade forgets about this demographic!"