I don't believe that Accurate sells the 2.5" round mufflers. They do sell the 2.25" straight thru (Magnum direct bolt in to OE, 2.25") mufflers, but they are not the 2.5". Their repro mufflers are the 2.25" OE style that are very restrictive and I have that style currently on the car.

Thanks for your reply.

EDIT:
I am currently looking for opinions on if the X-pipe/2.5"/6" diameter muffler x 14" long setup is going to create a deep sound, too loud, not loud enough if this is possible. If no one has this setup, then I will continue to guess at what length/diameter of mufflers that I will need and just try it out.

Thanks again for the reading and the replies.

Has anyone mounted the Dynomax Ultra-Flow Rounds to the rear beside the gas tank? I found this 2.5" (6" dia x 14" case).
http://www.dynomax.com/ultra-flo-welded-round-centered-centered-596.html

Thanks

I finally got around purchasing the 2.5" TTi X-pipe and tail pipes for my Challenger. I then decided on the Hooker Max Flow mufflers. I have read many threads on these mufflers and they all suggest that they are LOUD at WOT. Some of the tests show that they flow 521cfm each and the decibal reading at WOT is 120+, which is the same as a 2.5" straight pipe. Due to this, I wanted to add resonators beside the tank to try an lower the WOT sound a bit but I want to keep the exhaust as straight through as possible for a street car. I do not want to attract the wrong kind of attention and I do not want to wake up my neighbors, so a resonator is a must.

Mounting Resonators to the TTi Challenger tail pipes:

TTi told me that they do not make their tail pipes for resonators, but with the help of Eric from Classic Chambered Exhaust, he has helped me come up with a resonator that will fit onto the TTi tail pipes.
Most of the aftermarket resonators that I looked at had 2.5" ID bushings on both ends which will allow them to slide onto the outside of a 2.5" pipe. But, since there is only about 16-18" between the centerline of the muffler mounting bracket and forward before the tail pipe makes the upward bend to the axle, I needed a resonator that has a front bushing with 2.5" OD to allow the Accurate R/T exhaust tip to fit in this area. So Eric made me a set of resonators that have the 2.5" ID bushing on the entrance side to allow the resonator to slip over the TTi tail pipe, and he has added a 2.5" OD bushing on the exit end of the resonator to allow the Accurate R/T tip to slip over the end of the resonator. Mounting the exhaust tip onto the end of the resonator makes the assembly shorter and easier to fit into this area beside the gas tank. The resonator that Eric made is #25-RES-SPE. It is a 2.5" through pipe with a 4" OD x 12" body size. The bushings extend beyond the case by 2.5" per end. This is the first "off-the-shelf resonator" that I have found that will fit into this area for my 70 Challengers with R/T tips and TTi tail pipes.
I could not have STUFFED a longer resonator into this area! But this combination fit perfectly into the area beside the Challenger gas tank. There is plenty of room to go larger on the diameter of the resonator in this area, but no more room on the length.
Thanks to Eric at Classic Chambered Exhaust! Excellent customer service!!

The previous picture shows the TTi tail pipe installed with the Accurate R/T exhaust tip. I removed the TTI mounting bracket and made my own bracket that uses the U-Bolt bracket for mounting the exhaust tip. Now I have room for a resonator.

This picture shows the Classic Chambered Resonator #25-RES-SPE mounted to the R/T tip. Easy install!

This picture shows that I could not have stuffed any longer "off-the-shelf" resonator into this area beside the tank.
There is plenty of room to add a larger diameter resonator since the original muffler was 6.5" in diameter, but there is no more length without modifying the exhaust tip or the resonator.

I always run cheap glass packs (bullets) in the tail pipes on all my cars that have louder mufflers. But that is to control the drone. I haven't noticed much sound reduction, though.

Drone was one of my concerns too with the straight thru muffler. But due to Winter, I still have a few months before I can take it for a test drive. Since I had the time, I found a way to add them now when it is more convenient.

The Challenger does not have a lot of room to just bolt in a standard 12" resonator. I could have gone longer if I removed the bushings and welded them in, but my goal was to make it removable in the case that I wanted to go with a larger diameter unit later on.

It appears that The Cudas seem to have even less space in this area than the Challengers.

I was able to take the car out today for the first drive since installing the exhaust over the Winter. Absolutely no drone from idle up to 70mph with the new system!
(TTi headers & 2.5" x-pipe, Max Flows/2.5" TTi tail pipes, CCE 4" x 12" resonators/2.5" SS R/T tips)

The sound is LOW and deep at idle. The cruising sound was not as loud as I was expecting. It has a nice base to it and it got loud quick during light to medium accel. I was not able to test WOT today due to the cool outside temps and tweaking the cruising A/F readings. I can't wait to test WOT!

I like the combination of the Hooker Max Flows and the Classic Chambered resonators!!

Anyone ever seen these?

http://portermufflers.com/

I run Summits 3 inch stainless ovals.They exit by the rear wheel and are just mellow.might as well say straight thru but not loud.Plus they look great and the price was cheap.Rocky