If you use the "search" you will find a ton of threads on the On3 kit and many include dyno results.
If you surface the heads and re install with studs, felpro 9333pt1 gaskets and get a good tune you should be able to put down 425-450 rwhp at 14-16 psi. The TQ will be over 500.
This would represent the upper end of whats possible and you'd be one bad tank of gas away from changing head gaskets and eventually splitting your block.
You can install the ic wo removing your front bumper cover but it will be a hell of a lot easier if you remove your radiator, test fit the ic, then remove the bumper cover to do the trimming etc. I started a thread on how to do this wo butchering your bumper cover and there are a ton of pics on it.
92 Hatch On3 Turbo, T56
92 Vert 349 Lunati Stroker T5
87 Gt Eddy HCI T5
87 Notch in progress