Call Chris at Metric Motors in Centerville, UT and discuss this with him.
Google it.

He has these and many other types of Japanese motors that his shop
completely rebuilds for sand rail and/or aircraft projects he's been doing
for over 20 years.

My wonder would be: why doesn't he use one of these motors for the
"lively" Subaru-into-vanagon engine conversion business? As far as
I know, he hasn't and doesn't use anything for the conversion projects
except various kinds of Subaru's, out of which they can coax anywhere from
170 to about 600HP. They do all their own in-house dino testing/tuning.

bob