My 70 dart thinks she's fat.

My 71 Demon bracket car is 2500 lbs with a 416 stroker being built as I write this. I'm duplicating an engine that made 623 at the flywheel & went 9.40s in a 2800 lb car. My intent is to put the car in the 9's with the new engine, as the 408 has gone low 10's & it getting a little tired. My car has glass doors, hood, deck lid. & rear bumper with all lexan windows. The 408 is a screamer & I'm hoping the 416 will be even better.