On main frame there is a part that bolts onto the front corners, below Ref. 11 and 12 on diagram. It is called a hook tie down. This discontinued part number is D71177, 7/10/97 CNS
Ref. 3 and 3A, D75653, has a t-handle welded on the top. It is a push in style cap. Has a 1-7/8" Dia. neoprene base that would go into filler neck. L12291 is a twist on style cap similar to what would be used on a car. It is 2-9/16" O.D.06FEB97...glc