Considering that even the hybrid cars made by car manufacturers themselves are heavier than their ICE counterparts, I don’t think that by retrofitting an older car you’ll get a better result.

For example, 2024 Hyundai Tucson curb weights:

Heaviest ICE: 3663 lbs

Lightest hybrid: 3692 lbs

Lightest plugin hybrid: 4115 lbs

The biggest issue with an EV conversion is the weight of the batteries. For a lot of passenger cars, adding 500kg of batteries maxes out or even exceeds the vehicle’s gross weight.

I’d tell you one, but it got stuck on the event horizon of yo momma