I have no idea if XJSs came with gas or non-gas filled shocks but I do know that in the late 70s when buying a set of shocks for cars lots of times parts person would ask you want standard or gas filled. I think probably the late seventies was the transitional period to gas filled shocks, my guess the higher end vehicles used them first but they were available as replacements for most cars regardless of the which they had as OEM
Yeah, I can believe the E-type came with non-gas shocks since it goes back that far. Will they fit the XJ-S? Probably, at least at the rear. I dunno why anyone would go that route, though. Better idea would be to fit later gas shocks to your E-type!
With older and cheaper cars, yeah, you could choose between gas and non-gas shocks. By the time the XJ-S hit the market, though, any high-end car would come fitted with gas shocks. It wouldn’t make any sense for any aftermarket outfit to tool up to make a non-gas version, since presumably those high-end owners wouldn’t want to downgrade come new shock time.
Having worked on cars for a living in the seventies you’d be surprised how cheap some people were when it came to fixing their cars. It really hasn’t changed that much why you think some of these cars are in the shape they’re in. A lot of people drive cars they can’t afford to keep up.