sounds almost exactly like an 392 apache, very similar compression, cam, heads, CID, have you looked at a low miles take out engine?

The apache intake is better flowing out of the box plus it is plastic so light weight and keeps the air and fuel way cooler and as mentioned has the variable intake runner length. Last but not least they are cheaper. The only advantage of the 6.1 is it can be ported but its gonna need quite a bit to beat the apache intake and still going to put a ton o heat in the intake air. Another one thats better is the eagle truck intake and they are cheaper yet.