Custom rear bench for 88 Astro Cargo Van?

[[OCS]Viper]

I want to install a bench seat in the rear of my 88 cargo van. Something that can be easilly bolted in, and seat belts available. Also, if it can be mounted on tracks so it can slide forward and folded down to be used as a bed is a plus.

Does anyone have any suggestions? Since cargo vans don't have the anchor mounts for passenger seats, maybe there is something out of another vehicle I can use without much customizing?

Thanks for any help.