The 326 4 barrel manifold is different than the 400 4 barrel manifold.

The 326 2 barrel manifold is different than a 4-barrel manifold.

The 326 4 barrell manifold is the same as all the other 4 barrel manifolds that used the "non-Quadrajet" type carburetor (Square bore, might be an AFB).

Here's the square type:

http://i22.ebayimg.com/01/i/01/67/4b/b6_1_sb.JPG

Here's the Quadrajet type:

http://i15.ebayimg.com/01/i/01/6b/88/98_1_b.JPG

The square type were used on all V-8's with a 4-barrel for 1965 and 1966. I don't think they are all that rare.

As far as I know, the 326 never got a Q-Jet.

I hope this helped?

Q