Help with 70 Z28

[BCreekDave]

Watching this.
I think what we will find out is that the forging number is the same as that was the length, but the part number was different which determined the broached hole size.
The Z28 used the same manual steering box as the 6 cylinder Camaros. They quickend the ratio by using the longer 8 inch arm. The power steering cars used the used a specific steering box and the 8 inch pitman arm with a larger broached hole. The steering linkage is the same for manual and PS Z28's. Same with the idler arm. The non-Z28 PS cars used a shorter 7 inch arm with a different steering link that offset to the front to comp for the shorter pitman arm.

I think the "M" stamped on the arm in your photo indicated the manual steering '881 arm