Im curious if my trap speed is 108-109mph right now crossing the traps at aprox 4700 rpms, what will my mph be aprox with 4.11 gears.

 

There is no promise of a MPH increase. As a matter of fact, I quickly ran a couple of simulations with your setup through Drag2000, and your trap speed did not increase, and the ET suffered due to worse traction on street tires.

If your car can truly take advantage of spending more time in the upper RPMS, AND, you can hook off the line, then go for the 4.10s. But try to remember that you want to gear your car in a way that will place it's acceleration curve into the range in which YOUR engine makes optimum power.

 

From what I've seen, gears usually don't change your trap speed. One of my friends just installed gears in his Mustang and ran it at the track, his ET was better, but his MPH was about the same.

 

The gears are a true 4.11 btw, not a 4.10 Ill be using a ford 9" and I will be able to take advantage of the traction...