I think the coil only sends spark to your distributor, and with that, only matters when it is running.
Im thinking your computer. But either way, before spending money on parts be sure to follow procedures to test each one. For example, take your coil into a parts store and ask them to test it before buying another or you'll find yourself with a bunch of parts you do not need.
Look up some threads about the computer symptoms and see what you think.
..and to beat everyone else to the punch, ITS NOT A TRUCK! ITS A JEEP