only said about the type 9 mate as a know thats they fit not sure if the mt75 would or not but sure if it did thenthat would b a sure bet as like u say its stronger,

and as for the gear ratios it wouldnt really matter as in a sierra its the final drive u worrie about, i.e 5/6th gear and the diff ratio,

if the 5th or 6th gear ratio on a tranny box is the same ratio as 5th on a sierra box then all that would slow it down would b ur diff ratio but ad like to think that the diff ratio on a sierra would b alot higher than the diff ratio on a transit box so ud prob find that it would b very long legged and would b a very good conversion and am currently plannin this on my p100,