You got me... now to relatiate with math!
Assuming 1st gen Expy with:
Unlimed power
5500rpm RL,
Stock 4r100 ratios,
3.73 rearend,
265/70r17 tires
5500 rpm / .71 4th gear / 3.73 final drive = rpm at tire = 2076.80rpm
265-70r17s -> 99.293in circ = 8.274 ft *2076.80rpm = 9044.76 fpm = 3.254 mpm...