There's an kickdown rod that goes to the carb where it that has thread adjustment for the slotted part...
First you adjust the length of the middle rod that goes from the bottom of the trans to the top of the engine with the ball crank with a drill bit/rod in the holes to hold the bracket in relation to the throttle bracket....
Then put the horizontal rod that goes from the back of the engine to the carb and adjust the slotted part to where it bottoms out on the trans when the throttle is at wide open throttle - you don't want the linkage to prevent the throttle blades of the carb from opening all the way....
Get a kickdown linkage from a 67 - 72 318 or something close... The 2 bbl rod will be a little short, but there are tricks to extend it for the 4 bbl application - very easy....
It's explained at the end of this 4 bbl set up how to:
How to set up a Holley 4 bbl for a Mopar
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The red arrows and circles show where the two threaded adjustments are:
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Here's how to adjust it:
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