If you want to try and save some money, if your 84/85 module is still good you can get the 87 coil and buy an adapter base thru Napa for about $12 to use the 87 coil on the earlier module. I did that with on of my cars and it works great. The part# is ICA100. If your module is bad then caspers is the way to go.
I have the caspers adapter that plugs into your 84/85 harness and the other end plugs into the 86/87 coil/module. Worked perfectly. The 86/87 module that I had, had one of the bolts on the bottom ground off to make it fit my stock ccci mount. It was held on with the two remaing bolts but worked fine that way. If you want the adapter I'll ship it to you for $40.00 and then all you will need is the coil and module from an I/C car. Let me know if you need it.