Thought I'd write this here in case anyone was thinking about it. Pics are worth a 1000 words, so...
1. SRT spindles are compatible with regular 1500's. These are a requirement to mount the bigger calipers and have room to clear the bigger rotor (15"). As far as I know, 04-05 spindles are completely compatible with 02-05 1500's. Unknown as to whether the 06 SRT spindles are backwards compatible with 02-05 or strictly 06-08. Going forth with this swap ties you to a minimum 20" rim up front from then on (and then it has to at least be a factory spec 20x9 or larger with the right backspacing).
Not stock, note the difference where the upper ball joint goes
2. SRT-10's are 2wd, however the spindle is laid out the same (minus a difference at the top for improved caster/camber/handling) with the big hole
in the middle where the hub bearing mounts (uses the same exact hub
bearing, don't let someone try to sell you an "SRT specific" front hub bearing
for an inflated cost) and has room for for the front axle to pass through into
the hub. Theoretically, this swap should work for 4x4 1500's as well (but I
don't know of anyone who has tried it).
(Had to borrow an image from the pick-n-pull guys, couldn't find one anywhere else)
3. 2004 calipers are large 2 piston sliders. 05-06 calipers are larger 4 piston fixed. These are compatible back and forth, they use the same mounting ears on the spindle and the same exact rotor. Personal preference.
4. SRT lower control arms are different, but not a necessity.
5. Regular 1500 front sway bar and SRT-10 front sway bar - exact same diameter, no difference.
6. Coil springs - if you want a little front end lift with a little better handling, install SRT quad cab front springs. I found this out the hard way. My 2wd ended up a little nose high. SRT regular cab coils bring it back down and are stiffer for better handling.
7. SRT rear calipers are large 2 piston sliders. They are bigger than stock 1500 front calipers and use a slightly larger and thicker vented rotor. These are not a direct bolt on to a stock 9.25 rear (but anything is possible with metal fab skills). They are of course a direct bolt on to an SRT Dana 60...
8. SRT Dana 60 rear - damn near indestructible. 04's have 4.10 LSD, 05-06 have 4.56 LSD. Uses the same exact speed sensor and brake lines. Direct bolt in to your existing springs. One thing to note: if you aren't lowering your truck ALOT, don't get a regular cab Dana, they are lowered from the factory and are undersprung (leafs are under the axle tube). Dana from a quad cab mounts just like stock, in fact the SRT quad cab leafs are identical to regular 1500 leafs (part of how they managed to get some form of tow rating for the SRT quad). SRT regular cab leaf springs mount completely different, are shaped different and have built in wind up snubbers. Possibly useful, but most likely not a straight bolt in. Installing a Dana may require a custom driveshaft, especially in a quad cab (my driveshaft is 6' long...). SRT quad cabs use a 2 piece driveshaft.
9. Shocks - SRT's came with Bilsteins from the factory. They are excellent for ride and handling for a 2wd quad cab (only truck I can vouch for is my own). SRT regular cabs came with a dampener shock (also Bilstein) that goes from the top of the Dana to a cross member under the bed to reduce axle wind up. If you install a Dana and want to use this feature, you will need to weld in a bracket on the cross member, as non-SRT's don't have it there.
10. Rear sway bar - SRT regular cabs came with a dinky little sway bar; SRT quads did not. Most aftermarket rear bars will clear the Dana (all of them will clear a 9.25) and you end up with a better bar anyway.
I am always happy to answer any question that may arise.