No, you don't need it. It's only needed if you're running an SYE kit. SYE kits require you to angle up your pinion/axle; which often causes your shocks to come in contact with your axles. The Extension bracket moves the shock away from the axle enough to prevent this contact.
2003 Jeep Wrangler Sahara: RE 4.5" LA, FOX 2.0 Shocks, 35" BFGoodrich KM2s
2002 Jeep Grand Cherokee Overland: 2" BB. 31.5" BFGoodrich All Terrains
I am looking to get a set of RE 5.5" front coils. I'll trade my 4.5" or pay (not too much though) for them. Send me a PM.