DEI37 is quite correct in his statement that performance won't be up to the levels of the current M3. However, in terms of likely tyre footprint/technology, chassis composure and above all power delivery this will be considerably more difficult to drive than that current king of fast saloons.
In its day your new car was a handy little sports saloon - the state of the art, in fact. My Granny had one and she loved it. BMW never made a turbo for this model, though, and your car's after-market conversion - while surely a scream - will not have the levels of refinement you might expect of something made in Munich.
Soccerchamp, pull your finger out! I've had over 140mph (indicated) in my '89 325i touring on numerous occasions, although I do understand that such speeds are rather easier to attain on European roads...
