My previous posts were made here in error, so I apologize for that. This time around, I've been using Moltres in the UU tier so that I can make some topical suggestions here. As I expected, the situation is sufficiently different that my previous analysis requires lots of revising, though I won't be rewriting it or anything. I just want to address the characteristics of a sweeping set for UU.
Without Ninetales, Moltres has a harder time being a lethal sweeper, but all hope is not lost, for Sunny Day remains a valid option. I've been using Crobat as a partner, to Taunt common leads who would lay down rocks, trying to take them out using other members of the team, and with the entry threats gone, Crobat (hopefully) returns to use Sunny Day, holding a Heat Rock to prolong the sun. There are certainly many other options of Pokemon to fulfill such a role, and for some battles the chance to use the sun never really presents itself. Moltres is also a perfectly good user of the move, but it takes up a precious slot, and six turns is usually enough to dent the opponent's team nicely. My main objective here is to push for a Sunny Day set, in some form.
I've already touched on the awesome power the set holds. Assuming a Heat Rock is held, and depending on who sets up the sun, Moltres has 6-7 turns to shoot off fearsome Fire Blasts, utilize SolarBeam instead of the much weaker Hidden Power Grass, and Air Slash as necessary. Since UU is a slower tier, Agility really isn't necessary. A max speed, Timid Moltres moves faster than most of the things it will face. Flame Charge is an option to give Moltres an added jolt but each turn in the sun should really be taken full advantage of, and as stated speed isn't as critical. An option I've used is to use Substitute right before the sweep, preferably in front of a Pokemon that will switch out. This enables Moltres to survive scarf users, or muscle past things it can't OHKO.
Dragons are of little concern in UU, so Hidden Power Ice is unnecessary, as is Hidden Power Ground. Also, with auto-weather inducers much less common, there is a much lower chance that Moltres will find its sweep cut short; and more importantly, fewer times where it might get stuck with SolarBeam outside of the sun. If you can find a chance to use it, Roost is excellent, but I've decided to run with Fire Blast/Solarbeam/Air Slash/Substitute holding a Lum berry, since this is intended to be a forceful attacking set. Another option is to make the fourth moveslot U-turn, for use when the sun fades or an impassable wall like Chansey shows up.
The Stealth Rock weakness and its consequences are well-known and don't need further elaboration. Concerning the stall set, it's definitely usable, though Articuno does awfully well at it too. Choice Specs is an interesting option for added power, but Moltres really misses the versatility of having two or three attacks to choose from at once. Unless everything that resists fire is eliminated before bringing out the fire bird, I doubt the Specs set would work well in the sun, though the power behind a Fire Blast of that caliber would be a wondrous thing to behold.