There are 2 standard push rod lenghts. The short one is for power brakes. The long one is for manual brakes. Never use the short push rod and M/C for manaual brakes. You could have an instance where the rod shifts out of the bore and results in either a locked up brake pedal or no brakes (depending on where the rod goes). This isn't an issue on power brakes because the m/c is bolted directly to the booster.