when i had that cam, edelbrock performer heads and an RPM intake, i was trapping 107MPH or a slight bit less. I also have the 4.10 gears, so couple that with your 60', you should be in the mid 12s on average. Going to a better set of heads is really going to help your MPH. besides your shorty headers, whats the rest of your exhaust setup?
I have 2.5 inch flowmaster exhaust with single chamber mufflers and H pipe.
I'm outrunning most low 12 second cars to the 1/8 mile.
My 1/8 mile is high 7's@85mph