You will not lose any tq by adding longtubes unless you go with too large of exhaust piping behind the headers. My 03 hemi gained 35hp/41tq with superchips and longtubes as the only upgrades. Most guys see about 20hp/20tq from Superchips, so the other 21tq I contribute to the longtubes. If you only have basic boltons, then stick with a single 3" exhaust or a dual 2.5". If you plan to run heads and cam or boost/nitrous, then a dual 3" would be ideal. You need to move alot of air to use a true 3" true dual exhaust though, so I would stick with the single 3" or the dual 2.5". Also, you wont need a custom tune to use run longtubes. While you could squeeze a few extra hp out of a custom tune, it is not required with just the addition of longtubes.
2011 Ram 1500 RC/SB 5.7
1/4 - 12.04 @ 111.01 MPH N/A
Full Bolt-Ons, Modern Muscle Ported Heads, Moe's Performance XTP Cam, Hemifever Tuned, 4.56 Gears, Edge 3400 Stall Converter