The trunk lids have a different locking mechanism, that i know for sure. I DO believe the doors can be switched, but dont take my word on it. The trunk, probably not?
Yes you can switch the trunk lids. I have a 65 on my 66 right now. The only thing I had to do was make the hole alittle bigger where the tail light bolt went.
Both are interchangable from the cowl back. Seat tracks are mounted in a different spot and the rear bumper is different without a rear valance pan on the 66.