As long as the car is inspected and passed after the fact I don’t see why you would need certification for the actual conversion. Of course that’s a big risk on the owner, but if you’re pretty sure you know what you’re doing it’s not that much of a risk
Unfortunately open sourcing is not an option without certification, cause vehucles will not be allowed to go on roads.
At least here in europe
As long as the car is inspected and passed after the fact I don’t see why you would need certification for the actual conversion. Of course that’s a big risk on the owner, but if you’re pretty sure you know what you’re doing it’s not that much of a risk