Muffler choice is difficult due to different mods and your preference to the sound. I had flows on my '66 and got tired of the same as so many others. Went to the old glass packs and side exits. Love it and tons of compliments. On my '00, I just cut out the mufflers and ran the cats and straight pipes out the back. A bit loud, but I like it. If I ever have a noise problem, I will go with a straight thru type again. Listen to other Fords, search here for sound clips and take your time to choose so it is only a one time install.