I called SCP and asked Matt for the part number of the o-rings a couple weeks ago. He said he never uses o-rings. He recommended putting a nice bead of red rtv around the ID of the pipe's flange before sliding it on the engine flange.  I'm going to try that this fall.  Ultra gray and o-rings on my v2 failed miserably and trashed the front of my engine while we were in glamis last year...

Q gave me the following part number for the V2 pipe but never would send one for the V1. He did say the V2 ring would not work for the V1 pipe...
McMaster Carr V2 o-ring part number 9396K112