"just how brittle might the shell be and how crumbly the shock absorbing liner might be"I think I'd contact Shoei direct for that old of a helmet. I think I read that you can send a helmet to them and they will give it their official okie dokie if it is indeed crash worthy. And I'm sure they would be the only one that might possibly have pads for such an old helmet. That's what I'd do anyway. I do wonder though, if the pads are shot without any use, just how brittle might the shell be and how crumbly the shock absorbing liner might be. They would be the only one I'd trust the opinion on for sure.