'94 Rearend howling

Yes, the existing calipers and rotors are identical on the GT & V6, front and back. A Cobra rear axle uses the same calipers but you'll need bigger rotors.

If you do get an 8.8 rear end, here's a basic rundown on the V6 and GT/Cobra differences:

* The V6 center brake hose (from axle to chassis) is actually on the right side since V6's only have single exhaust. The attachment from the hose to the hard line on the chassis is also different. The GT & Cobra brake hose is on top of the differential housing, and uses a banjo bolt to attach the brake hose to the chassis hard line. The GT & Cobra also have a bracket & adapter that the banjo bolt screws in to - the V6 does not have it.

* This means that the hard lines on the rear axle are different, you'll need them as well with the 8.8 or you'll have to make your own. The rubber brake lines going to the calipers are the same on all 94-98 Mustangs.

The brake hard line under the car is easy to swap. It attaches behind the passenger front wheel and runs under the car to the rear axle. It's held on by plastic clips which you can save if you're careful. Be VERY SURE you get the bracket & adapter at the end of this hard line by the axle, or you'll be scratching your head trying to figure out how to connect the lines.

The bracket is held on by 2 steel rivets, you can drill them off to remove the bracket from the donor car. The V6 has the two holes that the rivets go into, but you'll need new rivets of course. You'll need some large steel rivets to attach the bracket, good luck in finding them. I fortunately am on good terms with a local mechanic; he gave me two steel rivets and lent me his large rivet gun.

You mention you might do a 5.0 swap later on. To be honest, if you're doing so to "save money" I would simply sell the V6 and buy a GT. It's a heck of a lot of work to do a 5.0 swap, and mine cost me a lot more money than I expected - and I had a donor car with all the parts already. Click on the "Cobra clone" link in my sig below if you want to read more about it. The reason I went through with the swap was to be able to say "I did it". Financially, it was foolish; but since I did it for the experience I'm glad I did the swap.