Yogi,
Were you able to find seals that are capable of handling the kind of pressures we put through these things? I could only find ones suitable for about 6-7 psi (low pressure grease seals)!
Jason: I didn't bother to mention that I have toyed with some awesome Teflon spring backed seals, but I had to machine a small spacer to get them to fit. The seals were like $13 @ piece and then with my machining work, it just wasn't worth it in the long run. I think you'll find that the o-rings will work well.