That Belleville spring will be correct. They can be hard to get in at times, I always fit new bellevilles as they break. I have at times had to compress the spring but usually can work your way around to get the snap ring in. The lower dished part of the Belleville sits down on the centre of the piston.
Now the clutches do come in two thicknesses early 67-76 in my parts list is around .060" 77 on are .078" You can use either but will need to get some clearance there. I'm guessing you originally had thin frictions being a 72 and replacements are .078"
Now the piston seal, inner is usually a round section o'ring, the outer can be a square cut or lip seal. The lip seals have a piston with a slight undercut on the lower land of the piston
Last edited by gregaust; 12-01-2013 at 02:39 AM.