For anyone that is in need of the 8 intake plenum o-rings check a good hydraulics store before you spend $13 a piece onthe merc ones. I gave them the Merc dimensions and they got them for me at $1.30 a piece!

McMaster # 9396K166 is high temp (red) silicone @ $0.67 each
McMaster # 9452K153 is OEM style Buna @ $0.16 each

I had been curious about that, I thought that mabe they were preformed to that shape. Thanks for the info as I need 16 of them.

No, they are round. Use vaseline to keep them in place when you are assembling.

Ed, The Mcmaster carr # you put in your post is the right size to replace the orings on the 500EFI? Thanks