Hi,
Been checking the archives as I thought I saw this asked once before.
Anyway for my 61 C30 Panel truck I want to run:
-a 292 with mild cam
-390 Holley on an Offy intake
-2.5" truck exhaust manifold
-SM465 4 speed with Advance Adapters OD unit (8 speeds- )

Q: The exhaust manifold has no butterfly-hot all the time.
Thinking maybe a stainless steel blockoff would take the edge off?
Q: 2.5" exhaust all the way back?
Any comments appreciated.
Thanks.
Pete

A thin blockoff plate would protect against exhaust erosion too, I've seen exhaust erosion / corrosion go right thru.

As far as exhaust, of course, I'd say 2.5" single all the way is a minimum for a healthy 292 - much over 200hp and you'd need more than that.