Try West Kentucky Tractor Parts? There were at least 3 loaders that were made in the USA for Kubota that could fit and you may find sub frames with them - the 1200 and 1800, and the Model 22 from ARPS. Also, figure out if you want to use the tractor pump (SLOW) or run a pump off the front spline (might come with the 1200/1800, the Model 22 came either way, but had separate reservoir on the right tower) and see if the pumps also come with. If you opt not to use the front pump, you will need a diverter block.