Start with a normal Porsche 912, an example with a straight body and a blown out engine or transmission is an excellent choice.
Open the trunk/hood, it's where you'll find all kinds of nasty, oily bits including an engine and transmission, the stuff that used to make the car fun and engaging. If you're familiar with Volkswagen Beetle's this should be like riding a bike.
Tear out the engine, this step, like opening the trunk should be easy.
VolkswagenPorsche engines of the era practically fell out of the car when you looked at 'em. Keep the transmission as that'll be useful to make the electric motor even pretend usable.
With a properly designed shaft-adapter a laughably weak 12 HP ES-31B Type 72-144 electric motor will connect to the input shaft of the Porsche transmission. Mounting brackets will act as your own personal hell in this instance.
Install in set of nine Interstate Ultima 12V batteries (or batteries of your choosing) above the newly installed motor and connect them through a...
AXE Performance series motor controller which delivers power from the batteries to the motor in a nice, civilized, extremely slow manner.
Adding a gauge to the mix makes make keeping an eye on the amount of available stored power much easier.
Ta-da! You have a functional, albeit slow as mud electric Porsche.