Hey Guys,
Got this from the book "The Sky is The Limit" ( Couldn't find the name of the author, so can't pay my respects ) Apparently taken from a Japanese Skyline sales brochure.
"The Type S is based on the GTS, and has alloy wheels, HICAS and the sport type steering wheel. The Type M is based on the GTS-t, and has 16x6.5 alloy wheels, HICAS, and the sport type steering wheel. The Type M, Type S and GTS-t have HICAS, the regular models don't."
"Options: Climate air conditioning, Electric front spoiler, Sunroof, Cruise control, Premium audio ( Kenwood / Alpine / AddZest), Rear spoiler, "Bug eye" headlights, Alloy wheels, Permium brake package."
Hope that helped!