The 86 has a headstart. The tail lights already match the 60's Batmobile headlights only upside down.
Of course for it to be the 60's version, it would have to be a convertible. In the end, I think that it would be pretty easy to make it a more modern batmobile runabout though. Maybe Toyota needs to get hooked into the next Bat movie and to a Transformer/Camaro-style badging version.
The DAMD kit in this
thread (and photo below) is a good start: