The FD started life in 1936 with a Hercules  DHX engine.  In 1938 the tractor was upgraded and the engine size increase to a DHXB engine.   In 1941 due to a shortage of Hercules engines the FDLC with a Cummins was made.  In 1945 it became the FDE with a Hercules DFXE engine. IT was made until 1952 and then the OC 18 came out.

Yes, on the 5 gear model the Gov is not timed.  The mag is driven by the water pump and that needs to be timed.

Cletrac sprockets are cast steel, they can be welded with any steel rod!  6011, 6013 7018 etc.

The Auto-Lite MZ-4098 was the first starter used on the HG, from SN 5GA000 to 25GA377. At SN 25GA378 they switched to a Delco 11029602.  I to would recommend Zimmerman's, they are very good to deal with.

Well Jack, that is a lot of work! But it should last a long if kept greased.

Yes. I would use grease there, as there are no seals to hold in oil.

The outside part of the stub shaft is cast iron. That does not take weld very well.  I would clean the stub shaft well with a wire brush. Then get some JB weld or similar epoxy and use that to glue the bushing to the shaft.

They are about 1/8" thick. which is not much. There are grease fitting in the support bracket, but most that I have come across have never seen grease.

For the EN the serial numbers should be 1B00 to 1B946. There is also a model EHG with serial numbers 1R00 to 8R52.  Both had Hercules OOC gas engines. Could your B be an R?

The sleeve is a press fit onto the sub shaft.  They usually wear through on the bottom and split. The support bracket will wear out of round as you say. They can be repaired by boring them out until round again then adding a sleeve to fit.

The gross torque for the IXK is 86 ft/lbs, net about 72ft/lbs. The later IXB was about 10% more.  This is at 1800 rpm.

Yes, leaving the bellhousing in place will work. I have done that.  If I could go back in time I think I would be kicking them in the but!!

I think there are some hidden bolts into the bellhousing that are under the front track supports. Makes for a lot of work to remove the engine!

That is good that you have the correct engine set up. Do you have the old engine?  You will need the bellhousing from it.  This is just a flat plate that is between the engine and clutch housing, it is unique to the Cletrac.  Zimmerman Oliver-Cletrac may have one if you need it.

The original engine was a JXD engine. It has a bigger bore than the JXC.  Both engines will fit, but there are two kinds of JX engines. Those with 3 timing gears and those with 5. Cletrac used the 5 gear engine and it has provision for the governor the 3 gear engine does not.  Look at the front gear cover on your JXC, if it is wider than the block on both sides it is a 5 gear engine, if only on one side, a 3 gear engine.  You could use a 3 gear engine but you would need to install some kind of belt driven governor or a foot gas pedal!