From the Mill Creek/Deep Creek Short Cut trailhead, hike north on trail 418.1A for .6 mile. The trail will intersect with Trail 418 coming in from the right. Continue west on swithchbacks, then north, then west again to a ridge where you'll intersect the Sneffels Highline Trail #434 in 1.25 mile. Head north following the dense, aspen-forested ridge upward. The trail will eventually head more NE into a basin at the foot of Dallas Peak, almost due south of the summit. This large basin trends NW toward a saddle between T.0 and West Dallas (PT 13,741). At about 11,300 - 11,400 feet, there are some camping possibilities used by some climbers. There is usually a sizable stream flowing down from this basin for water supply if needed. It's about 1.5 mile from the previous trail intersection.
The so-called "standard" route on Dallas would have you continue on Trail #434 eastward to climb Dallas by way of the SE slopes. Our route breaks off in the vicinity of the stream and possible camp area. Look for two tundra slopes, one to the west and another to the east a little that head upwards and appear to eventually converge below some prominent cliffs. Head up the basin about 300 feet in elevation, then turn and hike NE up a broad tundra embankment that will lead to the cliffs that appear to form the southwest terminus of the upper portion of the peak. As you walk up this tundra slope, it becomes steeper and the tundra thins out making footing more difficult on loose, rocky soil. Above the tundra embankment there will be a section of broken cliffs and ledges where route finding becomes more difficult. We found some cairns and followed them up to a large shelf just below the upper cliffs. This shelf allows passage upward by contouring NW toward a couloir with a section streaked in orange that drains the more gentle slopes above on the SW flank of Dallas. Once through the couloir, emerge into a large bowl of broken rubble with possible patches of snow. Elevation will be around 13,000 ft.
From the bowl, it's a quick and easy task to ascend another 600 feet to the Dallas west ridge. Once on the ridge, follow it eastward until it suddenly narrows to a series of broken blocks. A large gash will deter further progress east. To avoid the gash, follow these directions: Just before the ridge narrows here, look for a narrow cleft in the rock, just large enough for a body to get through, that will drop down onto the north face of the peak. Downclimb about 50 vertical feet diagonally along ledges, passing the head of a couple minor couloirs. There may be some snow here. The exposure here is very intimidating, but footing is generally secure, though care must be taken because of the gravel & sand on the ledges. Contour east about another 50 feet, then begin a diagonal ascent back up to the ridge crest. There will be another narrow cleft to navigate. You should come back out about 150 horizontal feet from the summit. The exposure of the ridge line remains severe. This is where some may desire a rope for protection, but there is little to anchor to or belay from. A large boulder may suffice. Since further progress is entirely horizontal, unless you place protection every 10 - 20 feet, a person would pendulum if they fell.
About half way to the summit, there will be a sloping, nearly vertical 7 foot wall. This is the only difficult & truly exposed move but was really no more than a 4th class climb. Shortly beyond this wall, the route eases and the exposure lessons and you can easily scramble on up to the summit. Congratulate yourself for completing one of the most difficult 13ers, then take a rocky seat to enjoy the stupendous view. From the summit, you can gaze down into the Blue Lakes Basin and Mt. Sneffels looms above all of this fractured and spectacular range. For the descent, return as you came, with care. Remember, most accidents occur on the way down. (As an additional note, it may be possible to stay on the crest of the west ridge and avoid the traverse out onto the north face, but since we had no beta on how we made this ascent, it seemed safest to return as we came.)
Links to other information, routes & trip reports for this peak that may be helpful.