Many on this site have the clutch on their tractors. Manuals for the clutch are reproducible. (I do not have one) the disks in the clutch are rare at this point, but can be relined and will be OK if the splines are good.
The clutches (according to some) are not quite as strong as needed if the tractor has had upgrades to power. But are very convenient for PTO operation allowing the PTO to continue working with the tractor stopped. Three routs to take depending on your M date of production Late 50 or newer and earlier than that. Early options Use an aftermarket M&W pump designed to be used on older Ms. Changing the gears in the front cover to Late M or SM gears is very desirable, some have had the gears strip, or keyways shear, from overloading a gear not designed to run the pump.
Type 2 is to use the front cover and gears from a late 51 or newer M SM SMTA. These have the heavier gears and the bolt spacing for the pump matches the spacing for IH pumps.
the third is to use a belt driven pump.
In all cases, a Belly pump with the guts taken out and a plate made for the resulting hole have been used for a reservoir. A spool valve setup is used to control the cylinders. JimN