l/cruiser gearbox

Hi guys
Just a quick ask about what gearbox is behind a 1991 1HZj 75 engined ute.
A mate is in the throws of getting a Chev diesel fitted to the above vehicle. As far as I know (or thought I did) these earlier models had the heavier duty box and the non turbo 1998 or there abouts and later had the lighter (Hilux??) box while the turbo ones had the heavy one. He is being told that he will have to buy the later turbo engined gearbox to handle the extra power and torque. In short is this true???
I was under the impression that his ute had the same box as the later turbo box with the possible exception of some ratios being different.

Help please and thanks in advance

Cheers Pop