All cars these days are unibody, no separate chassis.
I would build something like this to take the Spark EV's compact drive unit and battery pack: https://vanderhallusa.com/
Used '14 2LT w/ DCFC. +82K miles.
Mostly free charging! Only one LONG visit to the shop....
GM needs Modern Troubleshooting tools for Modern EV's.
3 step Trouble Tree, 1st try car died again, 2nd try not covered / cost $800. 3rd try fixed the problem.