PAUL T. - I'm sure some CC's came new on Firestone tires, but all the new CC's I was ever around all had GY's. I have seen several pic's of CC's with Firestone rears but can't remember ever seeing any Firestone frts in the 4.00/4.80X8 size but I'm sure there were some since your tractor has them.
But I will say one thing, those Firestones look to be in great shape for a 50 yr old tire where as my GY's on a couple of my tractors look like heck after 40 yrs. That "Gum Dipped" idea Firestone did back then does make a difference in how long their tires resist checking & cracking.
LARRY C. - Didn't you read any of my posts about using heavy, like 90W, gear oil in wheel bearings? I'm sure at some point grease when exposed to heavy pressure returns to it's primary ingredient, OIL, and if heated enough it will flow some. But haven't you ever taken something apart that has had grease in a mechanism and seen how the grease is piled around out of the way of bearings & gears? I've had elec. power tools like drills, saber saws, grinders, etc. so hot I can barely hold on to them with gloves on and when I take them apart there's piles of grease around the bearings & gears, but nothing on the wear surfaces. It doesn't really flow well enough to lube well.