I pulled my power booster from the attic tonight to try and measure the rod for you - but no luck. The rod is part of the back side of the booster and I do not have correct tools to disassemble.
I checked my repair manual and it references a different booster than other Pontiacs of the same year but on the exploded view of the master cylinder they reference the Tempest and Firebird together.
If you send me your email address I will be glad to try and scan the pages to a Word document and email them to you.
