identify correct model year heater box flappers?

[tcsracing1]

my 67S has what appears to be odd heater box flappers.

Would there be different designs over the years and would there by left and right difference?

here is my right and left.

[gled49]

the one with the lever attached would be original. the one with the spring is a replacement from a later year.

[mshaver51]

The swb heater boxes had 3 primary differences from those beginning late 68.

Swb cans had two pieces, with a separate section for the butterfly welded on to the main part of the can.

Swb had a clock spring on the opposite side from the butterfly opening, rather than a spring attached directly to the butterfly.

Swb had the cable guide on the end of the clamp, as yours appear to have, rather than the cable guide being welded on to the side of the clamp.

I believe it is accurate to say that the heater boxes were, in fact, left and right.

Does that help?

[tcsracing1]

so i am clear, the box with the spring is late and the box without the spring is early?

i need a left side heater box to be accurate for my 67S

[mshaver51]

This sort of detail is easy to mis-state and misunderstand, so i am trying extra hard to be clear.

The photos seem to show heater boxes from 2 different eras. The one with the coil spring appears to be later.

The other one should also have a spring, but it would be a clock-type spring on the other side of the box.

I believe that there is a left and a right side, because the bases have 3 bolts in combination with the butterflies, which dictate orientation. I could be wrong. You should check for yourself.