I have seen a number of 70 R/T's with either the body color or black painted rear tail panel that surrounds the taillights. Which is correct or is there some kind of date cutoff for this?
70 Challenger R/Ts tail panels were always painted body color. The only time they were painted black was on TX9 cars!
Common restoration error.
Challenger T/As tail panels were black.
BTW, your picture on the left appears to be a Challenger with a tail trim piece standard on SEs and optional on other Challengers by ordering A63. That panel is the rough gunmetal silver like used in non R/T grilles and rally wheel centers.
Another 70
Without
Again, you posted a picture of another R/T with the A63 or SE rear tail panel. That is correct for R/Ts that are either SEs or have A63.
Here is a thread from here on those panels.
https://forum.e-bodies.org/parts-misc-for-sale/9/about-the-elusive-1970-dodge-challenger-sewss-rear-finish-panel/10207/
Ah yes you are correct. Forgot about the SE's