Early '67's came with 350 CI engines and Yenko replaced the entire engine and beefed up the springs. As the 396 CI engine became available, later 427 conversions used only the short block as the heads and intake were identical square port items. Your best bet is to advertise on
www.yenko.net I've been out of town (Road America vintage races) and haven't checked that site, you may have your COPO on it allready.