I just installed my front ones last night. I don't have the instructions in front of me, but I believe the fronts are thinner, 6mm, vs 8mm on the rear.
Generally speaking, the taller (GS1) go in the rear and the shorter (GS2) go in the front. However dimensionally they will interchange so you can use the tall front/short rear or any combination thereof to adjust rake.
Where did you buy your suspension from? If Cruiser Outfitters it would have come with an install guide that covers spring & shackle orientation, torque specs, caster shims, and the rear spring isolators, etc. If you can't find it, email our tech team with your INV# and they can send you out another copy.
Long and short, you can re-use them, but you'll need spacers which should have been provided. Most don't re-use them, that too requires spacers which should have been provided with your kit.
Got the LC back on all 4’s today. Big thanks to @cruiseroutfit for helping me with all my questions!
Next week I’ll pull the the engine and transmission. Once I get everything out I’ll get it cleaned up and start replacing all the seals and gaskets. I’ll most likely replace the starter and alternator while the motor is out and I’ve got easy access.