Whats the redline on an 8v? on a valver its something like 7200 RPM.
because the gearing is exponential you can work out your top speed from lower revs for the same gear.
for example, using my figures..
2000 RPM in 5th = 45 ish
therefore..
4000 RPM in 5th = 90 ish
6000 RPM in 5th = 135 ish (i think its more like 130.. )
mine flat out has been in between 135 and 140 on the clock.. with more "rev's" left..
i just realised something else...
do you or your mate have different wheels? they'll mess up the speedo readout if wrong..