Not exactly an answer, but
To find the best main jet using MPH:
1. if not a full 1/4 mile, use the fastest continuous pull in high gear
2. start with main jets too rich
3. reduce the mains 1 size at a time
4. each size drop should increase the MPH
5. when it doesn't, go back 1 step to the previous jets

Summary: you want the leanest jet that doesn't drop MPH (the point where +1 rich doesn't help, -1 lean slows down). Depending on your gearing, air temp, water temp, scoop shape, exhaust, and about 10 other factors it could be anywhere between 11.8 - 13.5.