Leamans in PA is the guy I know of who makes the adapters, not cheap though. I wanted to swap a 4bt into a 450 I have, but the cost of the needed adapters was more than I would have into the engine and tractor.
Heres the link to his site:
Leaman Tractor & Parts - Home
Another option that would be cheaper would be to swap a 400 series engine in it. (DT414, 436, 466, etc.) That can be done using all IH parts, and parts for those engines are easier to find and cheaper than the german diesels