[Lynn Eades]

Unless you have a budget like a James Bond movie, I would agree with Charlie.
The seal system works well. You have 14 bearings with the 40mm bore, two with the 50mm bore, plus the 4 in your return rollers (something like 6308)
If you pop them all, clean them, oil them, then decide. They are big bearings, and even if not perfect will last a long time. (remember you track also has a limited life)Of as much importance is sealing them to keep the water etc out. so you also have to come up with 20 seals.
There are two seal systems (early and late), and you may have both kinds on the one carrier.
I do have some new bearings, but have pulled enough 65 year old good ones, to not have to use the new ones.
The bearings in the wheels are all 6000 series (metric annular groove) which is standard stuff, however the bearings in your fan extension are imperial, as is the one at the bottom of the steering column.
Having re read your post, it sounds like you have a different kind of bearing. maybe some photos might help.