I started running combines on a 125SPV. IHC had replaced a few chains with V-belts and had put on a wider rear axle in place of the tricycle tractor front. It would drive straighter than a 123 or a first 125, ie didn't cut around with every furrow or ridge, but otherwise was the same old machine. It could deliver a nice clean wheat sample but the feeder conveyer ran too fast and threw dust and chaff out like crazy. (That wasn't fixed until the 151 series) I don't think that it ran 1000 hours until it was about wore out. Over 100 grease zerks twice a day but the roller bearings running directly on the soft steel shafts never had a chance. The shafts wore down and would have had to be welded up to restore tolerances. Also no variable speed, just a four speed truck transmission with 3 somewhat usable speeds and, oh yes, chain driven wheels. If you really, really wanted to go between these three speeds you could buy different drive sprockets and cut and splice the drive chains to get a different ratio. I think we had three drive sprockets and picked an appropriate one at the beginning of each harvest and just drove around the field, none of this changing speeds every 100 feet. Life was simple!
That old 125SPV sure beat the old pull types, but today we run 8000 series machines with 45 foot heads and I don't plan on looking back!