Post your question to the holley forum,
forums.holley.com. Lots of good answers to questions on there. I have a 67, 383 with vintage air and am HIGHLY considering the sniper setup as well and would like to know this answer. How I interpreted the instructions, the existing a/c relay would work, just add the wire from the sniper kit. Also, I'm in KC too. I wouldn't mind coming by to check out the installation.