These manifolds are repop for the 327 manifolds and have 2.5” outlets. Studs are 3” apart. I’ll run a dual exhaust like the 1966 C10 with a 327. I’m not finding a heat riser anywhere but I’ll keep looking. Not 100% sure I’ll need a heat riser here in the warm weather of SC. Rock Auto sells a kit for the 1966 C10 V8 exhaust but they are out of stock. I have a first rate exhaust guy near me who uses a recipe card for these old trucks and so far has been great.
