Hi Pete! I can’t speak for the Kent models, but the Clark front seats originally came with lap belts. The rear seats did not have any belts, but it is easy enough to add them (lap belts). There are also seat belt conversion kits you can buy online that will allow you to add 3 point harnesses.
The Clark models generally had three configurations, the Executour, which was designed to be more of a mobile office; The standard model with sleeping for 4; and the ambulance. There is a rear bunk model, but as far as I know only came in the Kent models when they eliminated the rear door (72 and later).