hmmmm.. you have a big block with the flow 40's......i have a 350 with the flowmaster original 40's. i can't even go through a drive thru. i have to shut the car off to place my order. the original 40's are great sounding mufflers. i have 2.5" pipe dumped at the axle. the flowmasters create a whole lot of interior resonance. check out www.exhaustsoundclips.com.