Thanks Bobby -- I'll run those numbers at NAPA and see if I can get one.
Well, I bolted it all back together after coating both sides of the Clifford gasket liberally with Permatex Spray-a-Gasket copper stuff. Intake and headers went on (grudgingly -- next time I'm going to studs!), then I bolted on the Holley 390. It started up and purred. RPM was low at 600, and manifold pressure was 14"Hg -- should be +17"Hg-- but that's all fine tuning.
I got it down the block and around the corner and the power valve went out (silently). Lucky my neighbor came along so he could steer the pickup when we later towed it behind the GMC.
Now I'm thinking about an Edelbrock 1404 AFB 500 CFM.


I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.