I can't help with your 40/44 question, but I've got,a set of the HP2's on my 'bird. 2.5" exhaust, and some clearance issues with a tri 4 bar and coil over in back. They show as moderate/minimal on one listing, and aggressive/noticeable at the individual description. They were loud enough past 1/2 throttle I put resonators on, and its still pretty loud. And I'm deaf. So listen to the sound clips. I don't think I'd use these again.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I'd recommend checking on the Flowmaster site. It (as I recall) explains the difference of the series. They even have sound files for reference. In general I find thethat flowmasters have a more metallic sound overall. I have them on my bird, but can't remember the series #.

       A  L  A  N   F  R  A  K  E  S   ~  Tulsa, OK    

hi all,  i got a set of flowmaster series 44 mufflers today,  i had ordered 40 series,  any one know if theres much difference?,  would the 44 series  be to much for a 57 ford conv,  give me some advise so i'll know if i shjold send them bqck or ot.   thanks   jerry