Indy heads single water crossover /single plane manifold.

If it’s not all in at 36 until 5500 I bet that thing gets terrible mileage and builds a ton of heat driving 2200 rpm with like 24 degrees in it. You need to limit the mechanical timing, bump up the initial to where the engine wants it, and re curve the distributor to bring the all in timing in sooner. 3000 rpm would be late. 5500 is ridiculously late.