Hydroboost

[HotWheelsBurban]

There are a few different hydroboost push rod lengths. Originally, I had a hydroboost from a 1995 model truck K3500. I had the same issue you are talking about. I was not able to source a hydroboost pedal, so I removed the pin on mine and relocated it higher up so the pedal dropped. It worked great but the pedal felt too high. I replaced the unit with a 1998 K3500 hydroboost, and found that the rod was a little bit shorter. This dropped my pedal to where it should be.

There are also different styles of pushrod for GM HB on the 400s. As long as length is the same between old and replacement, you should be good.