Here is info from both the 67 and 68 (60-68) MPC. I did not look at the assembly manual yet - not handy at the moment.
This evidence leads the "jury in my head" back towards having more faith with Jim's suggested evidence.
NOTE: Jeff's picture, used to begin this thread, has an INCORRECT CARBURETOR ON IT so who is to say the linkage and/or spring haven't been altered as well...Still waiting on a few more unmolested original examples to show up. Hell hasn't frozen over yet!