Worth the headache?

At 155hp & 255kbs. Of Tq. that was stock for the '74 model year, I'd be hard pressed to actually disagree with the boards most famous 318 Na-sayer from Mass.

I normally agree with headers for mileage and power gains but on your year 318, I'd leave the stock exhaust manifolds on there and opt. instead for a full exhaust manifold back exhaust system from TTI.