The 326 used the 140 as the standard head and the 141 as the H.O. head. While neither were that great as far as Valve size etc... the comp ratio may be a little high as Q mentioned for the 350.

If you could find some large valve heads (better flow) and some that would bring the comp ratio for your motor in at about 9.0.1 or so... you should be just right. Even a later set of 6X-4's and have them milled down slightly would be good... and in a 350, a little cam goes a long way. The bottom end can be all stock, and you can work with the cam, heads and intake to really wake it up.

Yeah, just pick Q's brain on what he may
recommend, (just leave a little for the rest of us to pick!)

Later - Brett - 67 Drop top 455!