That is one of the best looking GP's I have ever seen

If you are doing the engien work you might want a tranny from a 1990-1991 SSE. They have a mucher steeper axle ratio 3.33:1 where yours is like a 2.97:1. I am sure you would enjoy that. Heck it's better than I should've done when I had my 99's trans rebuilt. If I'd had the L67 car more than two weeks when the tranny went out and if I had more knowledge on the Series II L67 and 4T65e-HD I would've had 3.29's and an LSD put in. At least I got all the updates done on the tranny and it has held out very well to the tune of around 280-290 hp coming through it.

Mike,

I've seen you on the cgp forum, welcome to the club. As far as aftermarket upgrades for a series i there isnt much out there, but a few of the guys here are looking into ways to eek some more power of it.

Again, welcome, i think you will find the waters a bit calmer in bonneville land (as opposed to gp land :) ).