I noticed the 70 chevelles have the T-3 lamps and my 71 chevelle has the power beam lamps and also in a pic on the 71 chevelle dealer brochour the SS chevelle has them in the pic,so I would guess that 1971 was the first year for the power beams.
Ron, actually the 70 Monte Carlo was the first Chevrolet passenger car to get the Power Beams. My theory has been since Chevrolet switched to the Power Beams for the 70 model year, some late 69 Camaros would have them instead of the T3's. Jerry's answer surprised me about May built 69's possibly having the Power Beams. I have found that just about all 1970 model Chevrolet cars that had the 2 headlamp system used the Power Beams, there have been a few exceptions where T3's were found in early cars. The 70 Chevelle still used the T3's as did most of the GM carlines that had the same 4 headlamp system. Last week I looked at a low mile unrestored 70 Corvette and 3 of its lamps were T3's, the other was a Power Beam. The owner could not say whether the light was changed or not. I am not sure what the norm was for Corvettes though. JohnZ can shed some light on that one. So your 71 Chevelle will have the Power Beams..............RatPack...........................
BTW, John, I have epoxied every good T3 I have now so as not to get any air leakage into them. Thanks for the tip!............................