Indy Halibrands

I picked up 2 of these Halibrand wheels with some "old" Firestones.
Anybody have an idea of the years this style wheel was used.

 

Are they 6-pin or 4-pin?

 

6 pin

 

Total guess. Early 70's CanAm or Indy car wheel.

 

Too cool.
The only thing more rare is the tall wheels Halibrand made for land speed cars (Thompson's Challenger, GoldenRod, etc.).

 

Any guess's about what years this style wheel was run?

 

Uhhhh, is my mic on?!