This sort of conversion gets coverage every once in a while and it's been neat to see old frames getting chopped onto new electric drivetrains. I spoke with one of the people interviewed in this article[1] a couple years back about converting an old truck I have sitting around into an EV.

The Model 3 approach takes their unified rear axle (motor,axle,wheels) and mounts it into an existing frame. Then you just need to find a place to stuff the batteries, retrofit some high-voltage electronics, and you're off to the races. One of the drawbacks of that approach is that it changes the stance of the vehicle, but for this Mustang that doesn't seem to matter much - it still looks classic.

Other converters either go for the high end with a model S and fit the motor into a traditional drivetrain for a sleeper build, or they go for the low end and take an old forklift motor and batteries and build what is effectively a street-legal golf cart. Prices range from $5-100k depending on your level of DIY and how dangerous of a classic car you want on the other side of the process.

[1] https://coloradosun.com/2023/06/25/classic-cars-electric-veh...