> Look up solvents for butyl rubber, vs neoprene, vs silcone
Gasoline attacks butyl rubber (developed in 1937) as well as natural rubber. Thus neither would have been used in a gasoline fuel system. Neither gasoline nor ethanol attack neoprene (developed in 1930). I"m fairly sure that before neoprene became available gasoline fuel systems were metal and glass with possibly some paper gaskets.