The tlok looks good. I'd try and get Ford Racing Gears as well. Sometimes the Motive or Yukon brands can cause whine when driving. Even more if they're installed incorrectly. Common saying is 4.10's for autos, 3.73's for manuals.
I'd also get a bearing kit to rebuild the rearend if your 04 has higher miles (+50k), and gear oil (Royal Purple is good) is needed regardless.
I would install both at the same time, they can be installed at the same time, any shop that tells you otherwise is bad news. Gears/tlok are probably two of the most effective mods for the v6's. While you won't gain hp, it'll definitely feel like you did...better acceleration, better launches, increased traction/handling, and two wheel burnouts
12 Black GT500 SVT PP l VMP TVS l JLT123 l O/R X l 28x11.50Rx15 M/T Street R's l BMR Suspension l Recaros
03 Sonic Blue 3.8 / 17 Magnetic Fusion Sport 2.7 EB