Hi Andrew - The number 7M4400 is just the part number for the D333 engine block, and the number 5M7844 is the part number for the cast housing ("cover") that contains the torque converter (torque divider).
The tractor Serial Number on the aluminium tag is the important number. It is located on the centre upper left of the engine block behind the filters, and on the RHS lower part of the dash, just above the floorplates, and on upper rear (vertical face) of the steering clutch housing (can't recall if it's on the L or R now).
However the ali tag on the rear of the steering clutch housing may be gone. There may be a serial number stamped into the metal of the S-C housing.
Regardless, the starter is easily found and a universal fit, it fits a multitude of models and brands (even Komatsu and Cummins!). It is a Delco-Remy model 50MT, 24V, CW rotation, 12 tooth pinion, and with an inbuilt pinion seal (this is known as a "wet" starter, to seal the starter internals from oil in clutch/converter housings).
Rare Electrical can supply a Chinese/Taiwanese "knockoff" of the Delco Remy, because as far as D-R are concerned, this type of starter is totally obsolete, and they give them little support. D-R want you to buy a Planetary Gear Reduction (PGR) starter, as this is the current technology. You can buy a PGR replacement starter if you desire, but it will cost more than a D-R copy of the MT50 from Rare Electrical.
https://www.rareelectrical.com/i-26...ack-tractor-d5-d5b-d6c-d6d-4n3313-6s9207.html
I uploaded your photo of the S/N tag and played with it in my photo imaging program, trying to bring out the original numbers using contrast - and I would hazard a guess the S/N is 76A3063.
There were only a total of 6061, 76A model D6C's built between 1963 and 1967 - here are the years and S/No's of production.
1963 - 76A0001 - 1117
1964 - 76A1118 - 2106
1965 - 76A2107 - 3593
1966 - 76A3594 - 5040
1967 - 76A5041 - 6061
