Hi Alb,
It's been a fun car and is a blast to drive with that engine, but admittedly I was looking for something I could drive more frequently throughout the year.
To answer your questions, it does have IRS and a 3.88 transmission. Discs all around and 185 x 15 tires.
To be honest, i don't recall what RPM the horespower rating was at. It was on the dyno about a year and a half ago up at Outfront Motorsports, where the engine came from. I got the rating over the phone.
The JPS spec sheet has more info on it. Find it here.