The 2nd design B1 piston is the one with the removable pressure pin, part# 126 270 97 32; 71 mm. you may need the plastic band support depending on your 722.3xxxxxxxxxx number.

Adjustment shims 0.5mm part number 000988 008015
1.0mm 000988 008006
1.5mm 000988 008024

The tool you are using is the right home made one, to use it, one complete turn of the bolt must equal 1mm of bolt travel. I had to buy a new one and more when one of my tool boxes disappear, Full with MB transmission specialty tools. If all else fails set the piston travel to .125”

I bought the self adjusting 3rd design with the intention of using them on all my rebuilt until I found out the hard way they lost there adjustment.

B1 PISTON