Small block intake

Use the factory intake and ThermoQuad you got and put a fresh timing set in with the three key ways in the crank sprocket and set it at 4 degrees of advance. If you want to try a pair of early rear dump magnum manifolds, I've got a set I'm tired of tripping over you could have for the cost of shipping. I know they work well on earlier trucks with automatics, and they work on some of the FJM cars, so they should fit a C body. Here's a pic of a new set for comparison.
Dorman Exhaust Manifolds 674-538
https://www.summitracing.com/parts/rnb-674-271/make/dodge