i have a 90 150 with a shot tranny, don't want to put the junk mazada trans back in it, is my money better spent putting in a zf from a 250, or the old t18, engine is a mild 351w, 4.10 gears eaton lockers

 

Why do you say the Mazda transmission is a junk transmission? Those that came in the full size trucks hold up a whole lot better than those in the mini trucks primarily because the full size version is a much heavier duty transmission.

Personally, I don't have issues with the full size Mazda transmission. They seldom fry and the main problem they seem to have is wearing out the 3/4 shift fork.

If I had to do a conversion, I would go the T18/T19/NP435 route any day over the ZF transmission even though I would no longer have an overdrive gear.