Not to get off-topic, but tire sizes go by the tread width (in millimeters), the tire height-to-width ratio (percentage), belt or ply material (radio is “R”, for example), wheel diameter (15 inche for M-body).
Correct examples are listed below.
In 1982, M-body the normal tire size is 205/75R15, using a 7.0” wide wheel.
Optional tire sizes are:
195/75R15 (using either a 5.5” or a 7.0” wide wheel)
205/75R15 (7.0” wide wheel)
My ’86 book only shows one available size (for '86 M-bodies): 205/75R15
FYI
195/75R15 tires are 26.52” tall (673. mm), tread is 7.68” wide (195 mm) and sidewall height is 7.68”.
205/75R15 tires are 27.1” tall (688.5 mm), tread is 8.07” wide (205 mm) and sidewall height is 6.07”.
215/70R15 tires are 26.85” tall (682.0 mm), tread is 8.46” wide (215 mm) and sidewall height is 5.93”.
215/75R15 tires are 27.7” tall (703.5 mm), tread is 8.46” wide (215 mm) and sidewall height is 6.35”.
Most tire size changes require a speedometer gear (in transmission) change or your speedometer/odometer will not read correctly. That does include a change to/from any the four tires mentioned above (or to other sizes).
BudW