I don't know whether you want to hear this or not, but I hope you get something from my experience:
Stock 360 Magnum, '01 with 4.10's (Off-Road).
I scored a full, new-in-the-box Flowmaster dual exhaust with tips and 50 Series Single in/Dual out on Craigslist for $120.00.
I had a local guy do the exhaust work. All this Fool had to do was join 2 pipes from the header to the mufflers, the rest was done for him as the Flowmaster pipes are mandrel bent, come with all the hangers and brackets and it fits perfect. The Flowmaster goes right from the bumper, over the axle and end about a foot ahead of the axle. Nope, he cried and whined that it was all wrong and he was going to do it his way ($$$$$$$) Long story short: it got done MY way. The 2 1/4" headpipes are joined to 2 1/2" pipes all the way to the back. I had him put an "H" pipe in. I've had my cat removed since day one.Flowmaster
Prior to this I had read what the "experts" on here had to say and they insisted you need un-restricted flow to gain power, so, I went with a stainless steel pair of Magnaflow copies (appear similar to your XR1's) with a straight through
design. What a MISTAKE that was. I previously had a Flowmaster 40 Single in/Single out that sounded amazing. I put these supposedly "deep rumble" things on my truck and it sounds AWFUL. I always got compliments on my Flowmaster sound and now the Hot Rod Dodge goes un-noticed and makes that typical "sputtering" sound that all the old V8 Dodges make. You know the one: that sound like someone spitting out a food wrapper after tearing it with their teeth or like the tailpipe is half under water.
So, with this true dual system having everything going for it maybe the sound will be all that's wrong with it? WRONG. Contrary to popular belief on here (and elsewhere) you DO need back pressure to build torque. I lost a significant amount of "lift-off" that a 5600 pound half-ton needs to get going. The power I lost got moved up to about 3700 rpm: Yep, that's right, exactly where 99% of the time a vehicle is never driven. Another downside was all the WEIGHT that extra pipe puts on a vehicle.
Given your usage description, the cubic inches, and horsepower, I think the 2.5's and a muffler with some back-pressure will be just about right for your engine if you want to maintain torque. As I said, I was expecting a moderate gain. I previously had a 318 2bbl in a First Gen and when I dualed it off with 2.5's and reverse-flow cans, the gain was noticable. Those straight-through "racing" cans I put on is causing the power loss, no doubt about it. One day I will cut that nonsense out of there and put a couple of Flowmaster 40's or 50's back in their place.
I took some pictures in the dark, not great, but you get the idea. I can do a sound clip for you ( I have the Flowmaster clip somewhere and can do a new one with this "straight-through" setup) if you want?