This is a Daihatsu engine rated for about 26 HP max, but I didn't find a dyno sheet for it:
432447-522447 drawings - Briggs & Stratton
Briggs & Stratton small engine sales by Tulsa Engine Warehouse
Seems like it'd be a pretty good replacement for a gas engine from a Metro, being 3 cylinders and ~1.0L (950cc).
The first link is the dimensions and the second link is the order info and a rep pic of it.
I'd bet with boost and some tuning, that thing could make a few more than 26 HP, and be able to haul a decent amount of crap in your truck while getting great efficiency!
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