In the 67-68 series there are two basic pedal support assemblies.
One is for manual brake, alone or with clutch, and the other is for power brake (PB), alone or with clutch.
It should be note that there are minor differences between assemblies created for service and those found in early and later assembly line supports which won't be addressed here.
Regardless if assembly line or service the manual brake version of the support has 4 captives at the firewall side while the PB version has only one at the top left corner.
This is a 68 manual brake and clutch pedal assembly. The 67 version is almost identical.
Two captives are shown with red arrows.
The PB pivot is shown with a red circle
The green arrow points to the clutch and manual brake pivot pin. Both the brake and clutch pivot here. In this case the pin is built into the clutch pedal (see later pic). If the car is an automatic and has manual brakes the pivot pin is a separate pin (much like a bolt).
Here I bolted a PB pedal to the
outside of the pedal support just to show how different the PB pedal is and how this changes the pedal ratio.
When converting to PB you remove the manual pedal and insert this pedal into the housing.
Here is the original, I believe, pedal on my small block 67 SJ clutch and PB car. [on edit] My apologies for the mixup. In the last few decades a few parts bins got mixed up, so my 65-66 pedals got mixed with 67-68.
The pedal above is for a 65-66 and shares most dimensions with the 67, except for the added side bracket.
The pedal includes the pivot pin for itself and the manual brakes (if so fitted). The pedal is often replaced after the plastic bushing degrades and eats through not only the pin, but saws through the pedal box assembly.
This, I believe, is the standard 67 pedal. I think it's based on the 65-66 pedal design and still has the original early hole and a new bracket welded to the outside of the pedal with another hole for use on 67s.
The area where the arm contacts the bump pad is also different as the 67 has a large bent over area, whereas the 66 looks cut off by comparison.