Matt, if I were doing it, I would rescue an HEI from the boneyard, disassemble it, shim the shaft for 0.010" play, grease it and reassemble with a new cap and rotor. I refuse to buy parts from KNOWN bad quality suppliers. Also, if I were you, I'd abandon my quest for an Offenhauser intake. Look for a Weiand Stealth or Edelbrock RPM. I've seen them used on ebay for under a hundred bucks.
I was typing while Chet was posting, but it looks like we think alike.