I've been able to compare the two springs and trucks in a salvage yard. The '05 spring fits into the '01 spring pocket after removing the rubber isolator. However, it isn't as easy as a direct swap. Some modifying is required.
The springs appear to be the same on on the lower end. However, they are
different on the top end. The '05+ 4WD springs are tangential on top, where the '01 has a bend, not quite a pigtail, that is held in place by the spring retainer clip.
The difference is due to the shape of the spring pocket.
'05 spring - not the same view, but you can tell what's different
The difference is due to the depth of the spring pocket and how the springs mount. The '01 using a spring retainer clip, the '05 using a longer sleeve that the spring slides around.
I THINK, that that 05 spring can be immersed in water up to the last coil and then a small spot can be carefully heated to put a bend in it to fit the '01 spring pocket. The water bath SHOULD protect the spring from over heating, while allowing localized heating where I need it.
Probably going to try this in the next couple of weeks.
Compressed, my '01 spring is 12.5" tall.
Compressed, the '05 spring is 16" tall.
The lift SHOULD 3.5" over the sagged stock springs currently on my truck. Guessing that is about 2" over stock height.
That SHOULD be within the adjustment capabilities of an aftermarket camber adjustment kit.