For low end torque a positive displacement blower is best. They produce maximum torque at the lowest rpm. You will never get the tires to stick with 800 rwhp on the street especially with a manual transmission. First, second and maybe even third will be useless. Every time you turn a corner and touch the throttle the car is going to want to go sideways because, unlike newer cars, traction control on these cars suck. It doesn't help plant the power. It only turns off the fuel.
I remember a post several years ago from a guy who was running around 450-460 rwhp with 4:10 gears. He reported that every time he turned a corner and every time he passed a someone the car went sideways. He was wanting a quick fix. There wasn't one except to learn throttle control. At 800 rwhp it will be a lot worse.
You said that the car is 99% street and that you had been playing with 600. I'm assuming you mean driving 600, not thinking about 600. If its the latter then be careful of what you wish for, you might get it.
ProCharger P-1SC, 9 psi, STD 396/383; Uncorrected 388/375; SAE 383/370.
Ret. USAF 1969-1973,1980-1996: Vietnam veteran. Aircraft maintenance. R & D, ICBM Operations.
Also own: 1997 Harley FXDWG, 1998 F-150, and 2002 Corvette LS1