Actually they are very simply constructed...at least in '64 and I think the '68 isn't that different. The challenge comes in matching old wood that has aged over the years. If there is a second one in the trailer you're looking at, it would be easy to use it as a "go-by".
Another option you may want to consider is having a built-in a Dinette instead. We removed our front guacho and built-in a dinette (click "photos" button below), it still makes down into a bed and is more functional during the day for our lifestyle.
A lot of folks have gone the futon route too...I would just be sure to attach it somehow so it doesn't move around while you travel down the road.
Good luck in whatever you decide to do ~
Shari
