You might not understand some of it, just because of the lingo
Old truck has a 13 speed tranny, new one has an 18 speed (more gears just means moving heavier things is easier)
Old truck doesn’t have a differential lock (most trucks you have a power divider to lock both axles, differential lock locks up one axle)
Heavier drive axles (carry more weight)
Just a few things like that, that most Eastern trucks don’t have
"chains on the dash" is a good thing to have.
Dusty, lots of ways to "heavy spec' a truck...rear ends start at 38,000 lb (pulling tandem trailers only on highway) rating and went up to 46,000 lb ( when I was trucking, might be heavier spec available now) for jerking super B's of various configurations on most any terrain. As Dave mentioned Transmissions can be rated by gear #'s, 10 sp,13sp, 15sp,18sp being the most common...also can be rated by engine ft lb of torque they can safely handle, from 95 flb( body jobs) to 156 flb. again super B's. Front axles can be speced from 9000 lb to 16000 lbs....Everything to make them withstand the abuse of us operators
All the above is OEM options and we added aftermarket skid plates & frame fishplates to "over engineer" off road stuff substantially...but every bit of "heavy spec" reduced the payload by a comparable amount so lots of head scratching goes into specing a truck out for specific purposes.