From what i've read and seen, 7.5's arn't good...
didn't the GT's have the 7.5 for awhile, when the 5.0 only had like 150hp.
When they got the 5.0 HO 225hp, they got 8.8's right?
I don't see why you'd put your faith in a rear-end that was replaced the 8.8.
it's not a big weight difference, gears and parts are easier to get for the 8.8 too.
The GT's come with T-lok from the factory too.
I spent $200 and got a stock GT rear, I'd love to put 4.10's in it later on.
I also wouldn't mind a 5-speed swap and split-port conversion