The spark plug wires are specific to the Duraspark distributor cap. And usually also a nice upgrade. You'll want a "electronic ignition" coil too. Your choice of any number of aftermarket ones. A stock one for an 87-93 Mustang GT works nicely. You'll need the Duraspark ignition box. Almost any parts store will have these. Tell them you need one for, say, a 1977 Ford Granada 302. Most of the replacement boxes are the same, but the parts counter guys need to be told something to go by.
You'll need to wire this stuff in. If you can work a wire crimper you can get about all of it done with only crimp on spade terminals. I used to grab junkyard harnesses but lately I've been getting ones with heat and grease damaged connectors. They're nice though as you can just plug everything right up if you used the stock Duraspark coil. You need only to patch two wires into your existing harness and really one those is optional. More details to be had here
. Though intended for slightly different engines, some excellent info to be had here
. look under "Ignition" And in "Electrical" too.