Steve,
C'mon buddy.
You're going to drop that tank into the car and try to get away with the T5? I ain't a mechanic, but sumpin' sure don't seem right about that... Besides, what happened to going with the small block?
I think a mild build up 351W is about as far as you'd want to go with the T5. A 460 would eat it for lunch.
Get serious about driving your Cobra and go with the 351W.
Steve