My secret wish for years has been to make a 'space cab' with my 49 3/4 ton chevy, affectionately known as Zip. The suicide 2nd door is half the size of the front door. I am getting to old to do it by now, I guess I would use lots of patch panels to get it. Has this been done yet?
So you want to make an extended cab with rear doors like a newer pickup.
I've seen several old trucks done this way, I don't know if any were 47-53 Chevy's, but I'm sure I've seen one at some time.