Sure it will. Sounds like a good find for the bellhousing and all that good stuff. Some folks really like those onan engines. Should have a 465 on the backside, so get the short adapter and you will be good to go for the drivetrain.
Hopefully you will get luckey and not have to sink a bunch of monies into it to make it run good for you..
Hey, Dieselcruiser (might spend more time on pirate)I think that is his website above, that deals with this motor amongst others, the price sounds right if it is what you need. Is this the same as the cummins 6AT? If so Royal Rose has a 55 for sale @ http://users.itsnet.com/rlrose/fj55forsale.html. Might see what he did and didn't like about it if its the same.