I just picked up this 91 GT. It currently has a 347 Carb'd motor with a C4 w/ Trans Brake, 4500 stall and a spool with 4.88 gears and all built( gonna have to switch to a 3.73 or 4.10). Has manual rack and brakes. It runs mid 11.s here in Vegas as it sits. My plans are to put a LY6 motor in it with a carb/heads/cam and a 150 shot. So far I ordered the AJE K frame and A arms and a pair of C&C plates. Headers and a JW Bellhousing to convert the C4 to work with the LS1. This is going to be a Drag only car. Here's some pics of it still all Ford...For now.

 

looks like you got a nice car to do a swap in, i used to have a 347 in my mustang and they have great bottom end but compared to the ls motors they def dont make near as much hp. Good luck with your build!

 

converting mine also..I had a 308 solid roller, vic jr head, vic 5.0...blah blah other ford crap...now doing a 346 trex ported heads, carbed, tremec 3550. I KNOW it will run better. lol