Stripped out 7-alike kit car with an all steel bottom end Toyota 4-AGE engine tuned to run up to 10krpm plus, with a centrifugal supercharger helping it push out north of 300bhp, 6 speed close ratio sequential box, road legal cut slicks, big brakes etc… Should waste just about anything else out there on the twisties!
Ultima GTR with an exotic engine, or at least not a small block Chevvy. Something like a BMW M5 V10, Audi/Lamborghini V10, or perhaps the 6.2 litre AMG Merc V8 from the SL63 but with added forced induction… NICE!
205gti with an Mi16 engine on throttle bodies, full roll cage, and track prepped.
Mk1 Golf with a 20V 1.8T engine (I know it's been done loads but I still want one!)
Supercharged BMW E39 M5, just cos the E39 was more of an allrounder than the E60 in my opinion, and the V8 is probably an easier engine to work with and get more out of. That and the E39 M5 was pretty understated and looked like most other 5 series, but with 400bhp it was pretty wild (yeah, I got to drive a couple of them, good fun too), but with 700bhp from a supercharged motor it would be crazy!
Lightweight mid engined kit car for use with a bike engine, but instead of some 1000cc inline 4, the 1700cc V4 out of the current Yamaha VMAX, tuned up a little bit! Should make it shift somewhat…
And loads of others, but my imagination is going to sleep right now…