You wanna check out the Beta 60, a marinized kubota engine. Its a bulletproof diesel with parts available everywhere. It’s motor mounts will fit our beds and is configured to be put in backwards. You don’t want to buy a new transmission as ours is the best but will you need an adaptor plate. I prefer this engine due to the low operating RPM’s vs the Yanmar’s and affordability of parts vs Volvo-Penta. Good luck finding a bad review on it.
I just replaced all my hatch’s with Lewmar Ocean series. You need the 60 series for the v-berth and the one behind the mast and the 40 series for the one in the galley. I had to trim the fiberglass ever so slightly on the galley one but the other 2 were drop-in. I HIGHLY recommend using Bed-it butyl tape on the install. We’re slipped in Waterford Marina in Houston and didn’t have a single leak during hurricane Harvey.