REengines are gonna have heating issues. They're air cooled engines. Not a lot of that in a rickshaw engine bay.
Anything beyond 30bhp is gonna be an overkill for 3 wheels. Unless we wanna make it look funky.
Still havent checked the legal issue with an engine swap on a road vehicle
Solar rickshaw could be a fun project.
200cc is gonna work just fine. We won't need a 390.
I don't think RE ever made any liquid cooled engine.