Shovelhead-style rear S&S cylinders do not have the stock-style wide base flange.
Shovelhead base gaskets specified as S&S are the same front and rear..

Head gaskets are made from made with Kevlar fiber-reinforced premium graphite material with a steel core, stainless steel fire ring and anti-stick coating. Base gaskets feature S&S Pro-Formance micropore compound proven to resist failure due to extrusion or blow out. Made in the USA.

1966-1969 fits H-D FLFB Electra Glide
1970-1984 fits H-D FLH Electra Glide
1966-1969 fits H-D FLHB Electra Glide
1979-1981 fits H-D FLHC Electra Glide Classic
1970-1972 fits H-D FLHF
1966-1969 fits H-D FLHFB Electra Glide
1980-1981 fits H-D FLHS Electra Glide Sport
1984 fits H-D FLHS Electra Glide Sport
1983 fits H-D FLHTC Electra Glide Classic
1984 fits H-D FLHX Electra Glide Special
1980-1983 fits H-D FLT Tour Glide
1981-1983 fits H-D FLTC Tour Glide Classic
1971-1978 fits H-D FX Super Glide
1980-1982 fits H-D FXB Sturgis
1983 fits H-D FXDG Disc Glide
1974-1984 fits H-D FXE Super Glide
1979-1981 fits H-D FXEF Fat Bob
1982-1983 fits H-D FXR Super Glide II
1982-1983 fits H-D FXRS Low Glide
1983 fits H-D FXRT Sport Glide
1977-1982 fits H-D FXS Low Rider
1983-1984 fits H-D FXSB Low Rider - Belt
1980-1984 fits H-D FXWG Wide Glide