Maybe that PCU was a front mount, I'd have to look in some books to find it, I recall a page that showed the various models, there was even a double "R" model, side by side, not sure how they powered both off the same output shaft. "R" in R7 model, I think meant rear mount and was for the XD7 Blade, so an FTD may mean a front mount, that would only require the front part of the overhead ridge beam set up, the mast, front radiator grill guard would have a bump out for the PCU, unlike the XD7 and a linkage would run along the right side of the tractor to engage, disengage the PCU, allowing for a rear mount PCU say for scrapers or other equipment, or a Towing Winch, which is different from a PCU/CCU, which are not suited for towing loads, the line speed is too fast.
I can't get over the price of these back then, not sure what the current equivalent model goes for today, several hundred thousand or more.
Earlier 3T's, production started of those in '44, ended in '55, 28,058 produced, somewhere in the last few years, they came standard with an oil bath clutch, the last few thousand made, there was also a field conversion kit to change them over. Some of these early ones also ended up in the military or government service, I have seen them with corps of engineer tags on the firewall left of air cleaner. Most government tractors were 7M's & 4T's. Yours may have been sold in '47, but produced earlier, possibly surplused once the war demand was over, 3T production may have lagged too, until the 4T purchase order was complete or cancelled, in '45 they were at the 5000+ mark, not sure if they built the whole 9,999 ordered. Civilian buyers could finally get new tractors again, new surplus tractors, with th war over. The lend lease act, had an effect, that and fear of market saturation with surplus, its sad to think, but they dumped some of these into the ocean at the end of the war, left them overseas too. Only one dealer, and or pioneer in custom caterpillar tractor building, Buster Peterson made a trip the south pacific to buy an allotment of surplus, as an investment for resale if I recall this correctly. Lot of fun history with these.
I don't ever recall seeing a 9U with a LeTourneau, dozer kit, earlier series yes, but it seemed 9Us were fit with caterpillar CCU's front or rear mount, or hydraulic blades per what the invoice said, was very common, lots of those around still, 9U, 8U's were highly regarded models, that were the basis for many later models that were also highly regarded, they built 29,000+ or so of them and another 11,000 8U's which are narrow gauge, must have been a good seller. Nice size too, for transport, working in the woods etc. Don't mind me today, was kinda stuck in the house this morning, but enjoy the old caterpillars, glad to be of help !