The trap speed shouldn't change when you change gears unless there was a dramatic miss-match at the stripes before. If anything I would expect the trap speed to decrease slightly. Steeper gears tend to have more loss and you may pick up a little in the 60', resulting in a slightly lower trap.
Anyway... if you are rolling 102mph, you'll be around 5800 rpm with 4.10's. Keep in mind the trap speed is an average speed from one point to another... so add another 50-100rpm to make sure you can run it out the back door.
On my car, I gained a solid 3 mph going from 3.27s to 3.73s. BUT, it's a bit of an exception in that I'm still on the stock converter. And stock converter + stock gears = a dog out of the hole. 3.27 rear gear + 2.84 1st gear is an EXTREMELY long first gear. The 3.73s helped a lot with that.
I'd guess you'd pick up 1 mph going from 3.73s to 4.10s.