I just use a standard relay, tape all of the spade connectors together (for strength), put the whole works into a small pastic bag, seal it with a dab of putty and Zip tie the bag shut, then Zip tie the whole works, up out of the way someplace.
One thing I do, that has saved me a lot of grief, is to salvage a whole box full, off the slotted plastic cable shielding from a junk yard. I don´t mess much with the stock harness, just add my own wires and protect them with plastic sheath, tie them to the stock harness with Zip ties.
I avoid tapping into the existing fuse box, I usually run a seperate (fused) circuit from the battery.
On my last XJ, I installed a small water proof pastic box up near the heater in the engine compartment, with a fuse rack inside. Found the box at a truck stop, parts outlet. Made hooking up the CB ( and linear amp), sterio amp and lights much easier and didn´t load up the marginal stock circuits.