[6pack] PDWA O-rings

[forzion at maine.rr.com]

I am about to take the PDWA out my early '74-Six (leaking) and note that different sources seem to specify differing sizes for the o-rings to be used. I believe the original o-rings were square cut but that standard round profile rings will work. Also, it appears VITON, EPDM, and some other compounds will work well. http://www.marcorubber.com/material_chart.htm There seems to be some disagreement between the Buckeye Triumphs site http://www.buckeyetriumphs.org/technical/Brakes/MCPDWA/MC.htm and the VTR site http://www.vtr.org/maintain/pdwa.shtml , regarding the correct size(s) to use. I realize different years use different sizes (early vs. late TR) but that doesn't seem to be clarified by either of these articles.
Also, any tips on PDWA piston removal (is compressed air the only/best way)?
Thanks for any help,
Dave
CF25194UO+TBI