How Do I Swap Brake Booster Pedal Pushrod?

I will spare you the run-up to this post; suffice it to say that it has been a nightmare getting this far with the replacement of my '78 D-150's booster due to lack of availability.

I need to know how to swap the pedal pushrod from my old booster (rusted-out, blown-out) into the similar-enough-to-work Cardone-rebuilt booster. The old pushrod is 1.5" -2" longer than the one in the replacement booster I have installed. Is it even possible? I have read that they just "pop out" with enough force applied, but trying to remove the pushrod from the old booster with force has proved futile.

Can anyone shed some light here, please?

Jeff
Author: carbdoc