I bet it would be faster then most other street cars. even a non prepped rb26 with that big of a turbo is good for 500+rwhp and 400+ ftlbs of torque.
I will say.... there are cars that are offlimits to swaps other then original, Cars like a yenko or any other very low production car. but in something like that stang..... if it makes it go fast im all for it. In fact im for anything that makes any kind of car go faster. weather it be its original engine or a transplanted.