Got to remember when the ttb came out no one had independent front 4wd in a full size pickup. Chevy 3/4 tons with leaf springs did not offer much more clearance between the springs and the bumpers with a straight axle and rode like #$@!. The upward wheel travel is more then the 3/4" between the bumpstop and the spring on the ttb. Ill admit it would have been great if they beefed up the 1/2 ton version with coilsprings, but I imagine public perception was that leaf springs equated a much more rugged design.
Dodges are also pretty horrible in the ride/travel daprtment, and they're also leaf-sprung monobeam fronts... IMHO before GM's IFS came out Fords were the best riding trucks, best handling too for the TTB models.
The 3/4" up-travel came from the OP saying that's what they ended up with cause of springs being too soft and thus sagging too much. But yes, you're right, from the factory it's quite a bit more than that, pushing 3" IIRC at the spring meaning about 4" at the wheel. Which is pretty good all things considered...
D50 with coils was what we had planned before a good-condition D60 popped up for cheap. Ultimately for our needs the D60 was the better choice, as it allows us to run air over soft leaves, whereas the coil-sprung D50 would have been either coils or air - IMHO blended suspension is great in that you get a vastly improved ride yet should one compoment fail (either cracked leaf or blown air bellow) you're not SOL too hard. Our coil-sprung D50 idea isn't dead btw, we got something in the works regarding that, but it's a long-term project and thus progress is very slow...
