Another factor that you might face while working with a new car is availability of a Cobra. Considering a very limited run this year and many of them already spoken for, you might have a tough time finding one.
I would say that if you "have" to buy a new one, a GT would be the way to go right now.
If you are still considering used vehicles, a 98 Cobra in good condition would be a great baseline to work with considering the 4.6 DOHC and live axle...
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"The Yellowjacket"
Ricer 1: What the heck was that!?
Ricer 2: I don't know. It looked kind of like a yellow SN95 Mustang.
Ricer 1: Nah, fast SN95 Mustangs don't exist... Must have been a mirage or something...