66 c10 with s-10 brake booster w/captain fab bracket

[Banjo]

Ive installed new s-10 booster/master combo to Captain Fab firewall bracket. Beautiful workmanship bracket. My truck must be missing something. I removed stock single jar master and associated factory adjustable rod.
I've tried 2 or 3 booster deals I've got laying around and while they'll bolt up fine, the brake booster rod isn't long enough to reach brake pedal leg where it did stock.
And their rods have round hole like they'd bolt to the brake pedal assembly, but the brake booster rod is about 4.5 or 5" short. I can't seem to be able to remove the brake booster rod in either of the 2 new booster assemblies I have laying around here.
If I could only remove the new s-10 booster brake rod, I could probably reuse my stock adjustable rod. But can't figure how to remove brake booster rod.
Do guys actually have to use a grinder and cut off the brake booster rods rounded end in order to tap the brake rod for threads, doing all of that with the bulky vacuum brake booster still attached.
I'm sorry to have to ask, I'm no seasoned pro, and didn't find search responses regarding how to marry the brake booster rod to the brake pedal leg APpreciate all help. Taking my 66 from manual drums to power disc drum, and this inability
To think my way out of this brake booster rod thing is hanging me up bad.