Look at the center console and down at the bottom , youll see the chrome spec plate . 1971 had lower compression figures across the board vs. 1970 (I.E. : BB's went from 10.25 to 9.0-1) . Also...h.p. ratings were expressed in NET for 1971 (which will be lower) instead of GROSS for 1970 (which will be higher).
You can also tell from the Dash VIN what year it is too.
Since you 'couldnt get the hood open'...i wont go into differences under the hood.
P.S. Have you been to Millers DognSuds in Ingleside yet ??
I thought all 1970 Stingrays had clear parking lens with amber bulbs, thats how iI always knew one from another. Did not know later 70 models had amber lens :surprised My 70 LT-1 must have been an early model