Advice on 440 into 74 Duster exhaust

'68-69 driver side fits EXACTLY the same as '70-73 (B-body HP manifolds). '67 is different and will only fit with a "B" block. By the time you figure out the value of B-body manifolds (whether you are buying or selling) and buying head pipes you're pretty close to the cost of headers. I run manifolds for the stock look plus I've always got a great deal on the manifolds.