yeah, I have the non-stainless steel version of these clamped (yes, clamped) into the stock system. Sound is awesome; yes, you do get drone but with 4.10s it's not a problem since you are out of the drone zone. And I like the drone!
However, unless you think you can actually buy the mufflers very cheap, I'd go full catback if i had to do it again. Or I'd get these welded in properly! I get a little leakage being that they are clamped into the stock system.
I too have the non stainless version of the 40 series,and had adapters made,and welded in to match up to the 2 1/2 dia.Then clamp the flows in aswell.
I personally love the sound of the flowmasters on mustangs.
No complaints here.
I've got some 2 chambers welded in along with an O/R pro chamber and it sounds great. Last time I went to the dealer I got told by multiple people that they loved the sound.
Flows sound sweet on any mustang, it really makes the car sound the way that it should have when it left the factory. Just get a catback system though, I think I paid $299 for mine from summit and everything fit great. By the time that you buy both mufflers and have a shop weld them in you will be in the $150+ range anyways. Later.
Flows rule!
That has to be the longest Ebay webpage I've ever seen. It looks like Fred Flintstone running...the same background, same pictures over and over and over.