Tony, think about fitting a new tranny input shaft seal if you split the engine off, it's a cheap seal, and replacing it is not hard if the tranny top is off, you would be disappointed if after a few hours driving the old girl you started seeing tranny oil in the clutch housing.

There is a 2 piece coupling on that input shaft that allows you to access the front input shaft cover of the tranny, you just need to be careful sliding the new seal over the input shaft as there is the risk of damaging the seal, using some insulation tape wrapped over the shaft is one of the tricks I've used, I'm sure other brighter folks here will have better suggestions.

To get the tranny top off is not hard, the fuel tank and fenders come off together, a smart fella like you would have it off before morning tea, and back on by lunch after cleaning any sludge from the tranny housing and checking the brakes and steering clutches.....

Don't worry, the next old Cat you drag home will be a piece of cake to restore.

Yes Tony, take the radiator off, it only takes a few minutes, there are 4 half inch bolts both sides, beware, like everything on a Cat, the radiator is heavy, so is that cross spring, you will need a overhead hoist of some kind, obviously check your thermostat in the upper water manifold once the radiator is removed, you will need a slide puller to remove the brass thermostat ring, it has 2 small notches in it for pulling.

With the radiator, you can either fit some suitable steel plates with 3/8" thread bolts to the sides up the top of it to lift by, or remove the radiator cap and fit some chain or heavy wire in under the bracket that the radiator cap screws to, that is what I did with my D4's, used that radiator cap bracket, obviously do not stand under that radiator when lifting it.

The trick to splitting the engine off easily is to first chock the front of the tracks both sides, then jack the back of the tractor high enough to get a pair of 6X6" or 8X8" blocks under the rear sprockets both sides, you then jack the front of the tractor up and it clears the main spring allowing you to slide it out. The repair book should have a photo showing that, before I split the engine off I put some blocks in under the front of the tranny, right near where the tranny bolts to the engine, just to help support the weight of the tranny when you remove the engine.

They may not be needed, but I believe you can never have too many safety chocks supporting a old Cat as you work on them, I'm always very alert when I'm laying under one! It's not rocket science, just go slow and steady.