So this morning I took off all the chains and put them in white vinegar to soak a while. I pulled the idler/tensioner pulleys off too and lubed them up good. Went over the chains with a brass bristle brush and wiped 'em off good before dousing them with my garage door lube Blaster stuff. Got out my dad's old grease gun and hit the zerks. Put it all together and pulled the cord. Started right up. Ran almost as quietly with the only the main chain turning as it did without it even on. Engaged the reel clutch and it slowly came around to turning. From the looks of the bed knife it is touching the full length and probably just needs to be run some more to knock the rust off the blades.
The differential on the rear axle freed itself up before even starting the engine, which was nice since I wasn't sure how it was going to react with power. Lifted the handle bars and engaged the drive clutch and the rear axle turned as it should, both wheels powering forward. I guess I need to plan an oil change sooner than later if I'm going to run this much more.
It is one heavy beast of a mower. I think it out weighs even my McLane front throw.
Thanks for the help guys. This has been fun.