When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
wow, I haven't heard of one of those in years, I used to R&R a lot of those, the main differences are; the motor mounts on the 391 were different, it had two off the bell housing and one off the front cover, which was iron, but I think the usual motor mount locations were still on the block, The other main difference was the crank snout had a larger diameter so the balancer, was specific to that engine, if I'm not mistaken the cranks were forged, old time hot rod guys would turn down the snout and have a cheap FE forged race crank, otherwise I think all else was the same, so, yes it should bolt in, but you have to figure out the balancer/belt drive configuration.
Why would you want to go to an FT - industrial engine - and not keep the FE?
If you do, I hope you have all the accessories for it....the crank snout (as mentioned by fitzmotor) is 1.75" and the timing cover, pulleys/balancer, etc, are prioritized for that engine.
Will the 391HD Ford engine Bolt up in place of a 390 to a C6 automatic transmission in my F350?
No, absolutely not. The FT engine mounts completely different than a FE engine.
All FT engines mount the same way, were usually installed in 1964/78 500 and larger series trucks, but...
1973/78 F350's made exclusively for U-Haul have the 330 2V M/D FT engine.
If you can find one of these (all have DRW, T-19 4 speeds and box van bodies), you will need all the engine mounting parts, bell housing, clutch parts and driveshaft.
Here's a pic (lower) of an F500 with a 330 2V FT engine mounting system (the caption should include F350). Upper pic is what your truck has now.