1986 Tiffin. The original owners manual was generic. It did not have the operation of the various items in the motorhome or chassis/dash items. It just gave you generic how to for camping. You can use a 1980 to 1990 Tiffin owners manual and it will almost be identical. The leveling system should be HWH and you can get the operators manual from HWH.corp. The Chassis should be Chevy. You will have to get a P-30 Chevy manual from either Chevy or another source. The appliances in the Motorhome also have their OWN operator manuals. Think of the old vintage RV's as residential homes. Very few homes have a "operator" manual. They rely on the various appliance makers to give the Home owner the install and operation manuals. Doug