This is a really cool idea. I never considered that something like this could happen.
I’m guessing all the parts that actually make the car go are getting replaced. I wonder if this will catch on and we will see a resurgence of old cars being retrofitted.
It's been a thing for quite a while. I want to say about 10 years ago I was watching a bunch of off grid YouTube videos and more than a couple people turned their cars into short range EVs.
More recently I've seen a few videos from a professional shop in Cali that does it for classic cars, also you have Jerry Rig Everything converting a Humvee.
It's been a thing and will probably end up being more and more common
On the whole, car should be lighter (-engine & parts,-muffler,-fuel tank) ... depending on # batteries needed (+ holding structure + cables)(might lose the back seat). Same Transmission/drive train needs.
Which mostly boils down to labor prices. You can build cheap EV conversions if you have free labor and don't care too much about range and charging speed