Here is a post by GregWilkerson Autolite 4300 Dashpot - #2 by catlover that shows the picture below describing the differences between the 67 and 68 4300 dashpots and their respective mounting brackets.
Also for completeness, here is a picture of an Autolite 4300 setup for a Manual transmission as instead of a dashpot, it has a solenoid. Note some A/C cars also utilized the solenoid to increase the idle speed of the engine when the A/C compressor is engaged.
Coach Jack