manifolds/headers

[kwmech]

No not the debate. A little brief history. 69 GMC 1 ton dually. Factory 350/400 converted to 400 small block with a serpentine set-up. I moved the engine back 1'' with the big block stands and am going to use the big block fan shroud. Seeing as how I have a large dimple in the engine stands, looks like plenty of room for some later model exhaust manifolds so the plug wires can come across the top. Any ideas on which cast iron manifolds will fit and get dececnt flow. I have been looking at the later model truck that has the O2 hole in the left side. (will be going to tbi this following summer) Any other ideas? Thing is, I do not want to keep running around buying manifolds to see what fits and doesn't. Some of these have to be special ordered. I may be open to some headers but will prefer the cast irons.