Identify this Farmall C

My friend just bought a restored Farmall "C" tractor. The serial number tag is a reproduction and has seven digits, which doesn"t make sense. I have taken the numbers 51131R3 then 2 26, off the engine block, and 251068-R1 off the differential housing. Can any of you IH guys out there help me identify what year this tractor is, by these numbers. I was unable to get the engine block serial number as it is behind the coil and had been painted over. Any help would be appreciated!

Jim
Those numbers with a letter R & a number at the end are part numbers.
After the "2 26" you mention should be a letter. That would be the casting date. J=1940, T=1950. Count up or down the alphabet from there to get the date the block was cast. In your case Feb 26.
There will be a similar number set on large castings such as trans & rear axle.
IIRC, Both U & V were used in 51.
HTH
Willie

Too many digits on the serial tag if it only had 5 digits its a C the SC started with 6 digits and never had 7. The # on the block would not probably match the serial plate. Your best bet is the cast code. 1+1+R the first number would be the month.Second number is the day and the letter is the year. Cseries werent made till late 47 and it usually was around a month till the castings were assembled on the tractor so the cast cade is always ahead of the production serial#. So the serial plate is not a true indication of the tractors age. Taller radiators and the grille are on the SC series. You will find cast codes all over the tractor and they will be different from one to another as they were made at several places. As with anything used you never know if or when any part has been changed over the yrs. So buy comparing cast codes you will be able to tell close to when it was built. I would ask former owner if they still have the original plate as the one now it not correct.

Hi Jim R: My second Farmall C is an early unit. Back when I bought it about 7 or 8 years ago, I made a list of all numbers I could see on just about every part. I don't trust the usual tag riveted on right side of box the seat is mounted on... too easy to swap from another unit. The numbers I trust a little more are those on the top plate over the rearend & tranny. Those numbers are right under your heel of your left foot when just touching the clutch with your toes.. Standing in front of the left rear tire and looking at those numbers I just mentioned under your left foot heel have the IHC logo above all other numbers. The second line is the casting code.. ( mine is 10-13-Q ) Just to the left of that and slightly below is a dot followed by 'USRC" and another dot....
The lowest line of info is I believe a part mumber and mine is: 351132-R1
I hope I didn't make a typo mistakes...

( Ah.. there are no 'lines' on which numbers are written.. I just used the term line & next line to seperate my info.. )
From my list of all numbers found all around the tractor, I am convinced mine is an early unit being about the 583 one built ( 501 was first number used ) which would be the 2ed or 3ed week of production.. all dates on casting codes vary from about 8 months before to 1 month before assembly on production line.. ( No just-in-time methods back then for parts ) Gotta remember IHC used Rail-road transport a lot and tractors could sit on flat-bed rail cars for a month if need be.. I rode a railroad passenger cars from near Sioux Falls SD to Chicago IL in 1945 and that took a long time and many switches. Didn't think we would ever get there so tractor parts traveled much slower from where made to where tractor was assembled..
Make a list of all casting codes and post it??
Might be interesting to compare to other early C Farmalls... ag. ret.