As a current owner of a Ford based TD, and the previous owner of 4 VWs, my 2cents agrees with PinkMG.
You say the frame is “no problem”, but realize that not only would it be a complete frame from stem to stern, but the body would have to be widened as well as lengthened due to the need to change the running gear to front engine/rear drive. Unless you are a fabricator or own a shop the cost involved would be like puttin’ a forty dollar saddle on a ten dollar mule.
I had to look for a while to find a Ford based TD since I knew I didn’t want a VW based. (been there, done that). If you’re willing to build a whole frame then the sky is the limit and I wouldn’t limit myself to a TD (even if I do love mine!!)