I did the trip because I have done almost all the other ACA routes and had started to do my own routs to discover new areas. The route takes about 6-7 weeks at a 55 miles per day average (I think). I did the route back in 2008. The route was "OK". It depends on what you are looking for. Back then I was on a "cross country" binge and had 7 weeks available so tried this. The scenery is only OK (typical plains scenery) with a few really nice areas. It is NOT scenic like the PC or Idaho or Montana.
Due to my schedule, I did it in two steps. Brownsville to Tulsa (where I live) in early May (two weeks) and then August 1 to end of August Tulsa to Winnipeg. With the winds being so strong out of the south, some days I would do 120 miles with little effort. I normally only due about 50-60 but when you coast along at 18mph due to tailwinds across Nebraska, it is easy to do high mileage. Conversely, when the strong winds would switch in late August, I would grind in my almost granny gear and be dead at 35-40 miles. I was on a schedule so had to maintain riding but would have stopped otherwise and it would have been an EASY ride.
Basically flat to gently rolling with a few hilly sections but nothing hard at all. Trip was a mix of camping and hotels. I had not stealth camped that much at that time but it would have been easy to do. Super friendly people, cheap prices, etc.
If doing in one trip, I would leave April 20-May 5 and be done about 7 weeks later (gives a few extra days due to spring weather).
I still have the route from Brownsville to Winnipeg. However, my route basically goes over toward Navasota, TX (bisects ACA ST), then pretty much north to Winnipeg. Other towns I passed through include Corsicana, TX, cross the Red River at a itty bitty bridge near Henderson, OK, Tulsa, Eureka, KS (ride along the TA for a day), Council Grove, Pawnee, NE, Council Bluffs, IA (on the L&C for a couple of days to Sioux City), Sioux Falls, Fargo, and Winnipeg.
I really drill down on the roads. My criteria are low-traffic roads, services, scenery/POI, distance. While this route is fairly direct, it does wander a tad.
I am sure I have the old cue sheets and/or GPS info somewhere. While it is been 9+ yeasr since I did it, I would seriously doubt much revision would need to be done since rural America is slowly declining in population unfortunately. Might need to reroute a few areas due to services no longer available and may a place or two around metro areas due to population increase but otherwise probably still valid. If you are
actually going to use it, I will scrounge around and look for it (it will take up to a day of digging around
looking for it (I have tons of unorganized boxes of research route material) so I don't want to do that unless you really intend to go on it. Hope you understand.
If you stick with US-83 you should be able to ride on the interstates. While probably legal outside metro areas along your route, I would personally look for alternatives as I don't relish all-day truck traffic, diesel, etc. You should be fine otherwise using an interstate. Between Brownsville and Sullivan City there are some alternatives. NW of Sullivan City, I personally would not ride.
Whichever route you choose, hope you have a great time! John