I power washed all the grease and oil off of this short block and it turned out to be silver. I assume that a C4 block is a replacement block from the factory? Were the C4 blocks that much of an improvement over the original or just minor changes? I picked up a non running 806D a number of years ago and was able to get the engine loose and running. In order to get it moving I had to rebuild the MCV, fix the shifting tower and rebuild the transmission cover. Just for fun I rebuilt the PTO, injectors, fuel pump and front steering bolster. I did hook it to a 14' 470 disk and work it a bit. The TA slips in low, the clutch is bad and it has a knock in the engine. So the plan is to do the TA, Clutch and install the new to me short block and see what else I can find wrong with it. The salvage yard claims 400 hours on the short block for what it's worth. I guess I can always convert it to a Cummins. Prior to this I had little to no diesel experience so I call it my Trade School Tractor. Had to borrow my wife's green tractor with a loader in order to lift it out of the shop. The engine p/n 607294C4 W 5 17 + L s/n B8D3611085 Tractor s/n 10816 about mid 1964.