I'm in the process of building a BEC "F1000"ish car using a CBR1000RR motor. I'm starting to get distracted with electric cars and have seen some Youtube vids about the newer Chevy Bolt (not volt) motor/transaxle that make it seem pretty awesome. I want to say it's under 100 lbs and has about 200hp.
https://www.youtube.com/watch?v=APhRPSdmdmkIt looks like you can get a used one off Ebay for $500 or so. Of course you need a controller and batteries. If you're not super worried about range, I would think 100 lbs of "hobby grade" Lipo cells could deliver the power you'd want. Most hobby grade cells are anywhere from 20 to 150 C discharge. It only takes about 100 cells to get to 400volts or so. If range isn't a concern I think weight could be comparable to a BEC.
Since I mostly do RC car (electric) stuff, it might be a more interesting option for me. I think it will ultimately cost more to do electric, but damn, the last time I looked at EV motors, prices were ridiculous. $500 for 200hp is awesome. Probably another grand or 2 for a controller, maybe a grand for hobby style batteries.