Center caps
#11
Well 1151 I found two sources that say the Impala's are 5 x 110 and two that say they are 5 x 115, ugh! Probably the 9C1 caps would require mods to fit and they are a bit expensive to experiment with. Another option to think about even though they are Ford parts(shocking I know), would be center caps for a Ranger truck, they are 5 x 110 and plentiful on e-bay. With a Chevy center cap decal they might give you the look you're after.
#20
I know you're being nice, my employees always razz me about getting old. I've never bought tires from e-bay, I keep things local since I know the owners of the tire shop, or should I say they've known me since I was in diapers. I've looked at tires on the 'bay and other online tire dealers, but the shipping is always more than I'd care to pay.