I would go for an electric motorcycle in your case, easy to add pedals to that and you could probably actually pedal it for a little while, and 40mph would be easy.
An electric conversion on a car will take a lot of effort and quite a bit of money but its usually about the same if you pick a really nice car or a really terrible car for your conversion. Perhaps your 84 civic wagon holds some particular sentimental value for you or perhaps its imaculatly restored but I suggest you pick a car that you will actually want to drive once its converted. I just don't want to see people put all that effort and time into something that never gets used! Maybe your 84 civic wagovan is that car
but remember it will still be an 84 civic wagovan when you're done, just slower.... and electric powered!
I picked the mini truck because its quite uesful as a small 4x4 truck for you know, truck stuff! And it makes a bit of a statement here in Edmonton Alberta where every other vehicle is a Ford F250 quad cab 4x4 diesel.....I'm not exagerating. That said its still a 20 year old mini truck, it makes my 2004 matrix feel positivly luxurious, which is why my next conversion will probably be that car.