WOW; I think those are great numbers. Shoot, my car was making that with a lid, catback, mid-length LTs, and crappy canned tune on 17" wheels and 335-tires (my brother's car put down almost 330/350 RWHP/RWTQ with a lid, catback, and OEM wheels/tires). It's still a pretty big car but I think she could get into the mid-13s stock; bottom 13s on DRs.
I'd like to see SSs put down about 370-380 at the wheel. That would make it pretty close to the 'Vette and would go a long ways to say how efficient that suspension was (from what I gathered, GTO suspensions soaked up a bit more power than a live axle

)