Could be like those Renault buses you used to see in Paris (may still) that were driven by inertial energy from a massive flywheel and relatively small engine to keep it spinning.
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Don't know if any of this info is of any use .The flywheel is 85mm thick and the cover almost certain was a SAE 3 which unfortunately went for scrap years ago .The recess for the clutch is 15mm deep and about 285 diam.It was off a boat 4bd1 engine that hydro changed to a 3bd1:o The garbage hanging of the FW was for forming SS boat rails:)
Noel
There is no hole for the clutch slave cylinder. It is external.
I've got a couple of photos here
http://www.aulro.com/afvb/isuzu-land...adaptor-7.html
The support lugs for the slave are on the MSA5 gearbox bell housing half, not on the engine half that you have.