['ol Pinion head]

Production '70 Pontiac A-body's were never factory equipped with Sport mirrors. Those do look like '71-72 Pontiac A/GP Sport mirrors, but w/o examining the black "gaskets" & the bases, they could be one of several other versions. On the Pontiac A-body line, Sport mirrors were first avail on '71 Pontiac GT-37's & optional on '71 GTO's. I can take measurements if you need, have numerous.

Have also gone through this mirror swap numerous times over the years on '70 GTO's. Recently, a local customer realized the factory Sport mirrors he had refinished & installed back in the '80's on his '70 GTO were ' 73-77 Pontiac A/GP mirrors. Stuck out like a sore thumb. Not just being mounted too far forward w the '70 side mirror mtg holes, the'73-77 Sport mirrors were also bigger, have taller bases & bigger mirror "pods". As that '70 was going through a frame-off, with extensive metal replacement, I ended up supplying the correct fitting '71-72 Sportmirrors, & the '73-77's ended up on a local body shop customer's later Monte Carlo.