Going to swap out the B1 piston tomorrow, ATF draining overnight to avoid dripping sleeve syndrome.
Came across this in an effort to resolve B1 assembly procedure, the pdf link above shows the alloy pin at the other end of spring v previous images.
Not sure if covered in this document as half way through.
http://www.w124performance.com/docs/mb/transmission/722.6/trans_722.6_ATSG_2004.pdf