GS is mostly a trim option and could have a 350ci. Stage 1 is a particular spec 455 with oversize valves and a special cam and carb.
'T' is the year code, the second letter tells you displacement and configuration. so 'TS' would be a Stage 1 spec 455 for the 1971 model year.
your 'TR' engine is normal A-body 455 for that year. perfectly acceptable as a Gran Sport but obviously not as desirable as a Stage engine.
you can install Stage valves in your engine and, obviously, there a better cam grinds available today.
The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
Government schooling is about "the perfect organization of the hive."
H.H. Goddard, Human Efficiency (1920)