I can't say either but you do bring up a good point, there were a few M5OD variants. '88 to 90/91ish was the first one, then very early 90's to the mid 90's (reverse cluster redesigned), then for a few years after that where certain gears were cut differently & the shifter was modified, up until '01 or so when the HD variant came out. I haven't played with the newer ones at all so I guess I can't say if the HD was only behind the 4.0 SOHC, and if so, were the internals the same as the 2.3 and 3.0 transmissions, or were those more similar to the units from the late 90's?
All that is probably irrelevant, my advise is pick the gear set you want and buy the rest of the parts based on that. Transmissions that originally were behind 4.0 engines of any year have slightly higher ratio 1st and 2nd gears - 4 cylinder, 2.9 and 3.0 transmissions have lower 1st and 2nd gears.