Richard.
It is obviously easier to install one motor, but as you are retrofitting running gear, it may be that a twin installation may be easier..otherwise a hole has to be bored through the keel which may be tricky, and also the frame may give a higher motor line than would be desirable.
Gosh..asking for a motor/prop combination recomendation on this site !!! likely to result in fisticuffs.
How about, as a train of thought..
Depends how fast you want to go…
OR how large the props will have to be to look right on the boat. I would think that you might like to decide on a twin or single prop setup first, then decide how big the prop/s will likely be to look O.K, and THEN fit a motor/s suitable for the prop/s.
The other thing is…how well does it float?? and will weight be an issue?? This may be a deciding factor on the gear? Picture ?
Ashley