[snapper]

Do have a good hard look at the gear ratios in the gearbox's.
The T9 box has better ratios than the MT75, the T9 from the euro V6 engine cars a bit better than the 4 cylinder cars but I don't know what the Merkura ratios are. The T5 which Europe knows as the one fitted to the Cosworth Sierra has the best ratios available and is the strongest of the gearboxes, I believe it was fitted to the Mustang over there.
It's all about first gear, MT75, 3.9. T9, 3.6. V6 T9, 3.3. T5, 2.9
Then look at tyre/wheel sizes and the Differental ratios, in the Euro Sierra we have 4 available ratios although there are more available
3.9, 3.6, 3.3, 3.14, in 7" & 7 1/2" crown wheel, push in or bolt on shafts and some with Limited slip (locker)
As a general rule the 3.9 & 3.6 are best for Haynes with car engines and the 3.3 & 3.1 better for bike engines