I've seen "kits" like that.. They are coil spacers that go under the spring and worse yet is the stud extender.
The stock shocks use a stud on the top and they use basically a 1" long nut with a piece of threaded stock. They they are doing is extending the stud of the shock so the shock won't be so short that it doesn't reach once you put on the spacers.
I've never used a stud extender and I doubt I'd ever want to. I was bad enough when I put a few washers on top of the bottom upper shock bushing to push the top of the shock down some...
Now, back to the lift kit linked above.. They do NOT know what an explorer is..
Do NOT buy this lift kit...
The key to my sentiment is when they say
(2x) 2" Rear Lift Blocks
- (4x) Extended U-Bolts
That is in addition to stud spacers...
You don't lift explorers by using lift blocks, the explorer is spring under and if anything, lift blocks will lower the frame.
Best, inexpensive lift kit is going to be f-150 spring seats (spacers) and AAL for the rear. If the suspension has quite a few miles on it then 2" spacers up front and AAL and possibly shackles in the rear will still be alignable. You don't "need" new shocks up front, but I would do it.. The rear shocks are fine with 2.5" or less lift.
~Mark
Edit: I found a picture of a stud extender that is 1 piece. I've seen them 2 piece too.