I've been watch this BMW i8 modded to take a Mazda 13B rotary engine and am learning a LOT!
From where and how to have metal etc parts 3D printed
to how to integrate electric motors with an ICE,
with everything working and looking professional.
It's a VERY good video series!
Probably the most relevant video so far is this one:
but he will most likely get the front motor working too.