For only $85 try it and post the results. I have a feeling it's not needed and there won't be a difference but who knows. I honestly don't know what it is and I haven't heard anything about it.
You shouldn't because I have one on my 84 and it works just fine
Only thing "wrong" is that the terminals are numbered for the 86/87 CCCI module, so follow the radiator shroud sticker arrangement and ignore the numbering on the coil.
I noticed some of these parts have to be ordered in (atleast in my area they do) That Accel coil is $99! They also sell an adapter for under $15... cheaper than Caspers? hmmmm
If you have an Autozone nearby you can order your parts on-line and have them waiting for you I took a look at the '87 control module, and some other parts and I'm happy to state they cover everything we need (crank sensor is available too!).
P.S. The Accell coil comes with the adapter plate to allow it to bolt to the 84/85 ignition module. I bought it at the local speed shop for about $80. I "think" they do mail order too. check out http://www.laneautomotive.com/ I am lucky enough to have these guys a mere 11 miles from home, in fact I pass them to and from work. It is always a struggle to keep the car from turning into their lot as I pass by It's really cool having a store comparable to Summit (and cheaper) that close to home, even though I live out in the sticks.
I wish we had shops like those in Hawaii. Everything's done mail order when it comes to our cars here. I mainly rely on other TR owners advice here. We do have a shop here that speciallizes in Domestic car items...though I sometimes get a face when I mention something about the car.