I have a simliar enigne. I built a n.a. 540, makes 680 hp. All good parts, AFR heads, 9.25 compression, .600 lift 238* cam, etc. etc.. Anyway, I originally had Gil WetOffshore exhaust on my 454 Magnum. I put that exhaust on this 540. I ended up with a bad reversion problem. The end result was switching to full dry CMI headers. Problem was solved but gained no noticable speed. Maybe 50 rpm, nothing major.