I just saw this thread, lot of good ideas and builds. I thought I'd post what I built for our 62.
It is built for sleeping two, and in a mind set to maximize the cargo capacity. ( no back seat = more room for stuff under the platform )
I started by removing the rear seats, and built a frame out of 1" square tubing and utilized the seat bolts for mounting the frame.
I wanted to be comfortable as possible while sleeping, so I made the platform as long as I could.
It came out to be 80" long, I'm a bit over 6' so it's just right. With the 4" foam it ended up being as tall
as the tail gate.
Also wanted a drawer to be as large as possible 40" x 40" x 8". Made it out of 1/8" aluminum to maximize the space.
At that size the wood would have to be 3/4" thick, lots of room and weight wasted on just the drawer.
The whole platform can be taken out in about an hour to re install the rear seats.
I still have to put carpet on the platform to finish the build.