Links have been corrected...
Here is some of the design considerations:
http://bbs.homeshopmachinist.net/sho...highlight=pump
Here is info on the pump:
http://bbs.homeshopmachinist.net/sho...highlight=pump
O-rings were #224, which are 2.00 OD, 1.750 ID, and .125 Thick. They were just the cheapest o-rings you can buy, I think it was $10.xx for 100 from McMaster Carr. They were machined .104 deep in the plate with proper clearance on both sides of the o-ring. Center section was a pipe plug with an o-ring for sealing.