How to put a 4x4 4spd tranny in a 2wd?

I just got a new motor for my '66 ford f250. The stock motor is a 352fe with a c4 automatic. The new motor is a 390fe. The guy I got it from have me a 4spd for it since he knew my c4 wouldn't hold up for long since the 390 cranks around 425 horse. The 4spd he gave me came out of a '78 bronco. Same truck the 390 came out of. Is there some sort of adapter I can get so the 4spd will work in my truck since it bolts to a transfer case?

A couple things don't add up.

1. The 390 didn't produce anywhere near 425 HP. With a 2bbl carb it was rated at around 255 HP, with a 4bbl it would be around 300 HP

2. The 1978 Bronco didn't have the 390 available, the last year for the 390 was 1975. The 78 Bronco has either the 351M or 400M

3. There should be an adapter available, I did a 302 to 390 swap about 20 years ago and in order to get the 3 speed manual to fit on the FE bellhousing. Try Advanced Adaptors, they'll probably have what you're looking for.