Thermo quad 6138s ?

The 6138 is for man 340; the 6139 is for auto 340. The same met rods & jets are used in both models. In decades of working on these fine carbs, I have never seen any difference to the idle cct. IFR will be 0.031-033". The difference could be one had a hot idle compensator, other didn't.
At some point, the acc pump rod & pump lever were changed, as described above. Also, with this upgrade, some pump shot is retained so that there is some pump shot added when the secs open. This does not seem to be well known. All the 9000 series carbs I have seen have this feature, but not sure when it started.