Lots of variables here with lift kits.
Springs are the same on the fronts for 1/2, 3/4 and 1 ton. Lift manufacturers just make common generic springs to fit each of these trucks and mass produce them. There are no different spring rates for each tonnage. Unless you order soft or firm ride.
Rear springs are the same but given two options of either the 52" or 56" lengths. Again, they are generic with no different spring rates on either to fit any rig.
U-bolts are where you need to be more specific with ordering a lift. There are a few different and you need to do measuring before ordering.
1/2 and 3/4 tons share the same u-bolts but there are two different widths of axles due to the First and Second Designs.
First will have a 2.75" axle tube diameter and the Second will have a 3" tube. Again, you need to measure to make sure you get the right u-bolts the first time.
Dana 60 fronts are by themselves as far as u-bolt sizes go. You need to know how long you need them to be in order to fit the springs, zero-rates, etc., that is if you're using anything other than just the springs.
Rear u-bolts is the biggest factor in being specific in order to get the right parts. You need to tell the person on the other line what you have. There are 3 different u-bolt configurations for our trucks.
1/2 tons use a 3" tube diameter.
3/4 tons use a 3.375" tube which is 3 3/8".
1 tons use a square-bend u-bolt with the threads pointing downward.
The 1/2 and 3/4 ton u-bolts are round-bend with threads pointing upwards.
You can use 3/4 ton u-bolts on a 1 ton rear but only if its a 14FF and you will need to get u-bolt plates, stock or custom made, to get those threads upward.
D70HD rears use the same type of square-bend u-bolts as the 1 tons and each are interchangable. The difference with these axles are the tube sizes of which the 70 has 4" gigantic tubes. The u-bolt plates under the tubes are the only differences between the 14 and 70. No changes on u-bolts here.
