5000 production numbers confusion

I purchased my late brothers 5000 a couple years ago, was told it was a 67 model and hadn't really looked at the production numbers until today.

It had developed a power steering leak under the radiator and the engine balancer was making noise so we pulled it in the shop this afternoon to tear it down for repairs.

While doing so I scratched off the numbers on the engine, trans and axle to see if everything matched.
Although the tractor looks pretty much original it shows signs of being repainted at one time.

Model code 51014C = 5000 all purpose, diesel, 540 pto, 8 spd trans
Serial number C138303 = US built around mid 1966, ok so it's a 66 model
Production number 6C24C = March 24 1966 afternoon shift

Figured I'd look a little farther so I checked the engine numbers
Engine serial number SR254618, R is for a 5000 engine but what's the S for?
Production number 7B21B = Feb 21 1967 day shift, looks like it's had a engine change, that's a bit of a surprise but unfortunately it's still a 233.

Back to the axle
Production number 6C30B = March 30 1966 day shift, that's not right
The assembly date of March 24 is 6 days before the axle was built on March 30

Anyone know where the production number are on a 5000 front axle casting. That'll till me if it matches the engine
It could be another SOS tractor thats been converted to 8 spd.

For now it looks like I've got a 5000 mutt to go with my 4000 mutt, I'm ok with that, just wasn't expecting it.

Have you looked at the flat spot on the left side to see if there's a date code there? It might be later than the one on the right which would make the one on the right the assembly date for the trans and the one on the left the one for the tractor. Some of the early ones had them in the wrong place.

As to the S at the beginning of the engine S/N, since it's definitely a later engine, maybe the "S" means that it was pulled from the assembly line and delivered to the dealer as a short block to replace one that was bad but still under warranty? That's just a guess and you'll probably never know for sure though.

Most 1965-1975 diesel engines that I've seen had a "D" after the series letter, like LDxxxxxx or NDxxxxxx on the earlier ones and CDxxxxxx or DDxxxxxx on the later ones. I've even seen some gassers with a "G" after the series letter, and at least one with an "L" for LPG (propane).

All I could find on the left side was C7015 which I believe is just the transmissions ID number.