I found an old post of yours:
https://www.ford-trucks.com/forums/2...-79-frame.html
You mentioned there was a level of interchange of F600 cabs and F150-250-350 cabs.
From what I have read on other threads, the medium duty trucks have a flatter floorboard, making it hard to source floormats that fit. Some have gone so far as to cut a LT hump out of a junker and install it in a F600 to allow LT floormats to fit.
I have also read of the isolators being different.
My intent is to take a short (129") wb F600 and install a dually bed. I know it's all doable, and donor cabs are just a CraigsList away, if a pickup cab will fit.
From what you say, and from what others say, the interchange is easily a pickup cab on a F600, but not so easy the other way.
And the front clip can go either way, from what I have read.
I have no idea about linkages for manual or automatic, but my hopeful guess is "no problem"
