My older brother had a late model Ram/Cummins which he used to tow his 5th wheel and he loved that truck. It was a great tow vehicle with a nice interior.
The new 10 speed is probably a fine transmission but I really like the classic Allison feel. I bought a 2021 Camaro with the 10 speed as my daily driver after I gave my 18 year old daughter my 2014 Cadillac ATS and I was going to buy the ATS replacement but GM was using the 2.7 4 cyl turbo gas that was designed for the light trucks and it requires premium fuel to produce more noise, less power, and less fuel economy than the 3.6 V6 in the ATS and the previous CTS that I owned. I much prefer RWD cars and I ordered a loaded 2021 Camaro with the 3.6 V6 just as the pandemic was starting. 335 HP on 87 octane with 32 MPG highway @ 80 MPH was much better than the CT4 with 2.7L four that replaced the ATS.
The Camaro has the lower torque variant of the Ford/GM cooperative 10 speed and it seems to be fine although it seems a bit "busy" at times with 10 gears. The Aisin is a very reliable transmission but it sounds like they missed the programming setup in that application. I have the 8L90 GM 8 speed in my 2016 Corvette Z06 and it works beautifully in that application even though there is a class action lawsuit against GM over the performance in other applications.
The Z06 comes with a 650 HP / 650 TQ engine and in touring mode the transmission provides silky smooth shifts and in track mode provides fast sharp shifts at redline while instantly downshifting when needed. I also plugged in a Range module into my Z06 which defeats GM's AFM system that drops cylinders under light load. AFM equipped vehicles modulate the torque converter clutch constantly when AFM is active to help absorb the additional engine vibration when it is running on less than its native number of cylinders which isn't great for the lockup clutch in the converter. I suspect Dodge does the same thing on gas powered vehicles with this technology, they cooperated with GM in developing the system and both use it on multiple platforms. I despise it, it really does little for fuel economy since it just reduces the pumping losses by reducing the amount of air pulled through a partially closed throttle plate under light load. It adds weight and complexity and at least in most GM applications, also restricts the range of control of the variable valve timing system due to the special lifters needed for AFM.
The Allison 6 speed doesn't shift as fast as the light duty transmissions but in GM's tow/haul mode (which is native mode for the Allison in other applications) it performs as close to a manual as I have found in an auto. In tow haul, the converter clutch locks with the shift into second and stays locked through other up and down shifts until speed drops enough to force it into first gear. When you run into one of those interstate backups where traffic is slowed to a near crawl because of an accident, tow haul with range locked in second and exhaust brake on allows you to drive it with one pedal like an EV.
The Hemi engines are fun to drive but they do like their fuel
The Ford 6.0, VT-365 in Navistar speak, seemed a lot less problematic with the Navistar programming and it led to an ugly corporate spat and divorce
The issues in Ford trim seemed far from insurmountable and it sounds like you have addressed them, congratulations! It is too bad Ford didn't, but all of the major automakers have had the MBA mindset since the 1970s with short term profits taking precedence over long-term including customer satisfaction. GM has certainly had their issues also. My first Duramax was one of the first 2001 (I took delivery in 2000) and I never had a problem with it but a lot of people went through a lot of injectors in the first generation Duramax. I sold it to a colleague whose son finally sold it with over 500K and he did go through two sets of injectors. The followup LLY generation didn't have sufficient cooling for those who towed heavy. I bought a 2006 LBZ when I sold my 2001 and it was a really nice generation coming just before more extensive emissions controls. Other than a mouse who decided to use the underhood fuse/relay center as a home/urinal, it was flawless for the 12 years I owned it. Hopefully my 2018 serves me as well and it has slightly better fuel economy than the 2006 even with the stupid DPF system. I think the better NOx reduction system using DEF allows them to offset some of the fuel efficiency lost to DPF restriction and regeneration since it can run much higher peak combustion pressures while still meeting NOx standards via the DEF/SCR system.
Finally, I also have a soft spot for IH products. I took my driver's exam long ago in my parent's 1973 International Travelall powered by a IH V392 and they later traded it for a 1979 Scout II. IH, like American Motors, was well ahead of their time with many innovations and the 1973 Travelall had a rudimentary form of anti-lock braking where the rear brakes were rapidly cycled under maximum braking to avoid lockup. IH was largely destroyed by a single CEO in the late 1970s who came to IH with no industry experience in agriculture, construction, or transportation; it was the era of believing a good manager could manage anything. Coming out of a high tech, no organized labor background he quickly managed to get IH into a major strike with the UAW which was a huge gift to Deere and from which IH never really recovered.
Rodger