I myself would get an complete engine from one of the Japanese importers. The early engines do not pull much money and you have a few importers not far from you. I have not looked at what they have in stock recently. But if they have one it sure beats getting one from the States for you. Any used engine from either of our countries world have allot of miles and not be any better than what you had.
The other option would be a later 24V engine but will need its wiring swapped in as well.
As it is your heads need to come apart enough the clean the oil passages and check for scoring in the cam journals. I would keep them as spares.