Do a compression test and also a leak down test on the motor to make sure you don't have any problems internally. Flow the fuel system to make sure it is flowing what it should. Double check ignition timing. etc.

What's the elevation at your track? How's the air quality there? If the air down there is pretty bad then that may account for your times and MPH being slower than I think they should be.

For comparison...I had a stock stroke .030" over 440 in my car, weighed in at 3700#, single dominator on a Team G intake, OUT OF THE BOX Indy SR heads, 262/268 at fifty solid roller, 14.5:1 compression...it was a street driven setup with mufflers on race gas. 727 w/ 5k stall, 4.10s and 28x10.5 DOT tires. Ran 10.40s at 129 mph.

It may be a combination of bad air and the fact that your car is a 4 speed that's throwing me off. CHIP