I can't remember, but one of the pistons has a spring against the cover (B1?), and the other, no spring (B2?). I did this job, and it was not hard at all. I had to make a tool to pull the sleeve, and it worked like a charm. There is a thread here somewhere, I will see if I can find it. The challenge is getting the "dogbone" to stay in the right place while inserting the piston in the bore. I used red grease. You won't know if you got it right unless you remove the valve body to see up inside.
Here it is:
http://www.peachparts.com/shopforum/diesel-discussion/385909-300td-b2-piston-replaced-still-no-forward-movement-3.html