Wanted Right side 340 HI-PO exhaust manifold

On the other hand if you're worried about the heat crossover, you could just block it off. The horsepower and heat imbalance that you percieve would be offset by a car with irritating starting habits (assuming a stock carb). One would assume that this is a basically stock engine with exhaust manifolds as opposed to an after market hi-perf engine with headers. A stock engine means factory tolerances, which are notoriously generous, so 10 H.P. either way from side to side probably is not that remarkable or possibly even accurate. Interesting thoughts though.......
Daryl