Well, the numbers just don't add up for a FORD T5.
But they DO add up for a GM Borg Warner T5.
Assuming 26" tall tires and 2:20 rear gear and 4800 rpm = 55 mph in 1st gear.
Transmission Ratios, standard issue Ford T5:
1st gear is 3.97
1st: "3.97" 2nd: 2.34 3rd: 1.46 4th: 1 5th: 0.8
RPM\MPH 1st 2nd 3rd 4th 5th 6th
1000 9 15 24 35 44 0
1500 13 23 36 53 66 0
2000 18 30 48 70 88 0
2500 22 38 60 88 110 0
3000 27 45 72 105 132 0
3500 31 53 84 123 154 0
4000 35 60 96 141 176 0
4500 40 68 108 158 198 0 (this aint near 55 mph in 1st)
5000 44 75 120 176 220 0
5500 49 83 132 193 242 0
6000 53 90 144 211 264 0
BUTT, if it's a BORG WARNER T5 GM trans!
1st gear is 2.95
Borg Warner T5 with "2.95" 1st gear ratio (2.20 rear gear).
RPM/MPH 1st 2nd 3rd 4th 5th 6th
1000 12 18 26 35 48 0
1500 18 27 39 53 71 0
2000 24 36 52 70 95 0
2500 30 45 66 88 119 0
3000 36 54 79 105 143 0
3500 42 63 92 123 166 0
4000 48 72 105 141 190 0
4500 54 82 118 158 214 0 (Thats close to 55 mph in 1st).
5000 60 91 131 176 238 0
5500 66 100 144 193 261 0
6000 72 109 157 211 285 0
With BMW running gear that trans has GOT to be a Borg Warner. If it's a FORD T5 the rear gear would have to be like 2.00 for 4800 rpm to equal 55 mph.
This is the best calculator I've found BUT, you have to "register" to use the site. No cost, no personal info, but kind of a hassle. Turn off "Pop Up's" or it won't work.
http://www.smokemup.com/auto_math/mph_range.php