Actually, the KCS Southern Belle scheme was never applied to Trinity 5161 cu. ft. hoppers. It was applied to Gunderson 5188 cu. ft. hoppers, and to the ARI (nee ACF) 5200 cu. ft. hoppers, both of which are generally similar to the Trinity cars. However there are differences in details between all three, like the jacking pads, side stiffener ribs, and the shape of the car sides at the end slope sheets.
To answer your question, neither Lionel car is a 100% accurate model, but both are close stand-ins. The DM&IR did in fact have ACF hoppers, I believe for hauling the binder used in making taconite pellets. They did feature the large arrowhead on the side. Lionel even has the correct earlier side stiffener rib, the single angle welded lower on the car side. And it looks like they even took a shot at getting the correct outlet gates on the hoppers. The issue is that the DM&IR prototype car is of a smaller cubic foot capacity, I think 3560 cu. ft., so it is shorter than the 4650 cu. ft. Lionel car. The net result is that the model is a bit longer than it should be, and the hoppers are spread out further than on the prototype.
The primary issue with the KCS prototype car is that it's of the through-sill variety, like most modern covered hoppers. The Lionel model is of a traditional side sill style ACF car. Of course, the prototype is also a larger capacity car, so the car length will be compromised somewhat. The other obvious nit to pick is that Lionel used the same type of combo gravity/vacuum outlet gate on the KCS car when it probably should have been a typical gravity only grain type gate.
Follow the links to see examples of prototype cars.
So, neither car is truly accurate. They are both close in many respects, certainly plausible adaptations of the existing tooling. Obviously, you'll need to decide how strictly you want to follow the prototype.
By the way, a good way to check something like this to go to a photo archive site like RRPictureArchives.net, where you can search by railroad, then car type or road number range. You can check if a specific road number is correct for a paint scheme, but you can also browse around to see if there is something similar.
Hope that helps,
Jim