I was thinking more along the lines of a simple/reversible modification like existing propane conversions. I know there are people doing body off Tesla conversions and the like.

I envision batteries + motor/bio fuel cell in the trunk or something. I believe Mazda is looking into electric motors inside of wheels/hubs and Honda was exploring hydrogen in push rod engines.

I come from a hot rod family, so I understand your point on classics. Perfect example is a T-bucket vs a Model T.