I'm new to boating ....

Looking ahead (hopefuly later rather than sooner) I would like some options
on re-powering a 40' houseboat. Two options I can think of a

1/ rebuild the existing 318's and use different transfer (transmissions?)
and drives. Drives are Dana which are obsolete and parts are expensive! Are
there any Chrysler 318 owners who have done or even researched this?

2/ convert to outboards. What sort of reinforcing would need to be done to
the transom, hull, both? What else would I have to consider? Considering
houseboats can be like a sail, what size would I need. The 318's are 220HP
ea. What would a o/b for this application cost (cdn please).

Anyone have any other options/ideas (this should be good) or has any
experience with either of these projects?

The houseboat is a 40' 69 thunderbird drift-r-cruiser.

Steve E L