M5OD is a base model number
M5OD-R2 was larger version used mostly with V8 engines
M5OD-R1 was the smaller version used with 4cyl or V6 engines, so Rangers
Its common to abbreviate each version as M5R2 or M5R1
These were unique in that the Bell housing was part of the main transmission housing, can't be removed
This means each M5R1(or R2) is made for a specific engine
There were 4 M5R1 engine versions
4cyl SOHC Lima engines
2.3l DOHC Duratec engines
3.0l V6 Vulcan engines
These 3 versions used same gear ratios
4th version used different gear ratios and fit 2.9l, 4.0l OHV and 4.0l SOHC engines
The 4cyl Lima, 3.0l Vulcan, and 2.9l/4.0l versions also came in 2WD or 4WD versions
2.3l DOHC never had a 4WD version
So overall there were 7 versions of the M5R1
There are no different numbers for these, all would be listed as M5OD-R1(M5R1)
So a used model would need to be listed by engine type and 2WD or 4WD, to find out what it fits
There was an M5OD-R1HD
It was only used on 4.0l SOHC engines, in both 2WD and 4WD versions, same as the 2.9l or 4.0l OHV M5R1, interchangeable, internally the same just had and extra bolt hole on bell housing
The M5R1s for 2WD didn't have a speedometer cable hook up from 1998 and up
4WD versions never had speedometer cable hook up, it was on transfer case thru 1997, but gone 1998 and up