Very few people restore and upgrade cars like that. That would be a minuscule market. Maybe 1,000 customers per year doing custom EV retrofits to old classic and hope-to-be classic cars.
But your everyday driver / commuter car? No way in hell would such an investment be warranted in a worn-out econo-car.
My daily car is a 1990 Mercedes diesel
It just died...looks like fuel tank clogged up with black gunk
Need to remove the fuel tank clean it out, replace filters.
I suspect the fuel pump and injector pump will need a rebuild.