can anyone please help!?! need engine ideas for a mustang 345

i have a mustang 345 missing a engine. what are some ideas for a replacement?. i have heard people say everything from a kubota engine to a engine from a ford escort. what one would someone in my situation suggest? if i went the kubota route what engines do i look at? i cant seem to find a ford 4cyl like it had anywhere. please help!!!!

Kubota is a good place to start. They have an internal govenor, the biggest issue is how is it coupled to the pump.

Kubota V2203 would likely be an engine of choice. Bobcat used this engine in a lot of models from the late '90's on. Usually, they are rated at around 45hp, bit more power than the old Ford Kent motor.
From what I have seen in other posts, old reefer units (from semi-trailers) seem to be a popular source of these engines used.
Good luck!!