It has all the correct appearances of a 3600 gasser. Air cleaner in the left side hood,
Exhaust pipe farther forward than a 65-75 model,
One piece grill, flying nun fenders, correct tach direction.
Remember they didn't give the decade so the 7F01b could be June 1st 1967 or June 1st 1977 (maybe even 87 - not sure on that new) but I would say it's a 3600.
The serial number codes will also be hand stamped (not cast into) a flat spot on the bell housing just above and aft of the starter. See photo for example.
Tell your friend he bought an outstanding small tractor!