First things first - 1971 options may or may not apply to 1972, and 1972 may or may not apply to 1973. Never assume an option or package is the same for all three years, as likely it's not. The content can also change during the model year.
Swing over to the Wiki page and download the salesmans' facts books. They are a wealth of information.
https://wiki.7173mustangs.com/
It's important when reading the the option lists, to realize what is *not* included. For example, a common assumption is the the woodgrain center stack was part of the Decor group - it wasn't. The only cars that came factory with the woodgrain center were the Grande' and sportsroofs equipped with the Mach 1 Sports Interior option.
1971 Decor Group was a mostly interior option. It did include some exterior items, and the available upholstery choices varied depending upon the body style and model. 1972 & 1973 Decor Group was an exterior option.
1971 Convenience Group - note that auto seatback releases were deleted and credited back on early 71 cars. IIRC it was a parts supply issue.
1971 Instrumentation Group. For 71, if you wanted a tach, you had to order the Instrumentation Group. The M1 Sports Interior option had the triple gauges with a clock, adding the Instrumentation Group bought you a tach.. Ford fixed that for 72/73.
