Question of a different caliPer

[silvia200zx]

I'm puttting 300zx calipers on my 240, however one caliper was leaking so I'm rebuilding them. I need the seals between the two halves of the caliper and the dealer doesn't seem to know what I'm talking about. I ordered a rebuild kit and the all the piston seals were there, but not the ones for between the halves. The calipers are aluminum and I'm pretty sure they are the 26mm variety however I could be wrong, how do I check to see. The slot for the rotors is about 30mm, which allows some space if the rotors are 26mm, if the rotors were 30mm I don't think they would fit, it would be VERY tight if they did. Anyone here know what I'm talking about? I need to know where to get the seals for the two halves of the calipers, and knowing what size calipers would obiously help. Please let me know how to figure this out. Any info you provide is greatly appreciated.