Moonroof, Navigation System, "Special" package, at one time the "performance package", and I'm probably missing a bunch others were the only options on the M.
Leather, Autostick, 3.5L, and a bunch of other features were standard on the 300M, it and along with the LHS (which became Concorde...then decontented heavily, unless you got the Limited) were Chryslers flagship cars. With the LHS putting more towards comfort, and with the M more towards driving dynamics.