Actually, most manufacturers will have a version or another.
I believe the idea was started when RV manufacturers started using roling chassis vs custom frames. That was back in late 60s.
Or could have become routine when I am enforcement became irritated enough when converting passenger vehicles.
Now, near every chassis, cars included, that has room for extra 'stuff' has something available that aftermarket uses. Ford & GM are extensive, as is Mopar, for van and pickup.
~SD
