i have an '82 with the back of the cab out and plan on putting seats in the back. would the rear part of the cage (meant for a 4runner) fit for the rear part of the truck?

No, the 4Runner rear kit fits on top of the rear fender wells. It would not be long enough to reach the frame. I would consider using All Pro's flat bed kit. Jon uses with setup on his truck and has a small kid seat in the rear.

Did Jon also run an internal cab cage? Do you have any pictures of his truck.

He also has an internal cage but it was built before we had our cage kit. It's similar, but the front legs go though the dash.

Here is a shot

and...