Bullet style GM sport mirrors on a Square

[burban nate]

I was at my local Menards today and saw what I figure to be a '75-'76 ish C10Silverado short box stepside painted flat black. It had a factory tach. It also had buckets and woodgraining in the interior. Something I find odd was it had 2nd Gen Firebird/Camaro style bullet sport mirrors. Only thing was the bases looked to fit the truck doors perfectly and kept the mirror tops level. I think it looked really sweet. So now I'm wondering if this was ever a factory option? Or did this guy just do a really good job adapting them?

Thanks, Nate