65 AMC Marlin

you need to do the paperwork with the DMV if you want to sell it
without it you do not even legally own the car
you just have possession of it
on line it will not go through as you found out due to the non standard VIN number
you will need to go do that in person, just bring a tracing or the VIN # with you and some pics of the car, the classic value will not be much as that car is a 1 or 2 not a 4 or 5
then you could even get it running and drive it for a bit