[Hcb3200]

Finding just pushrods is not easy. and when you get boosters they often do not come with them because the theory is you use the one you are replacing.
If they gave you the wrong one in a KIT then I would work with the vendor to get it corrected.

Since I was a budget build and cobbled parts together for one of my truck.
I just went to pull a part yard. found a booster with longer rod. Just took the rod for I think a dollar.

Then just ground the end to the exact length I wanted.
I did it on the bench with small adjustments each time till i got it where it was spot on for my master and booster. Then smoothed the end to almost a polish. rounded just like the rod that was missing.