That's probably a Ford 9N (9 for 1939) tractor that the owner dropped a flathead V8 into. Not Ford stock, but quite a few have been done that way. A V8 from anytime in the early Ford V8 era, 32 to 53, would work. Again, none came with the dual carbs, but it was a common speed mod. If you're going to go to the trouble to drop a V8 into a tractor, might as well goose it up a bit.
The suggestion of using a Ferguson as a basis is a good one. Interesting fight between Ford and Ferguson over patents on the three point hitch.