I was looking at trailer wiring harnesses today & noticed that there isn't a plug & play for my '88 ('91+ no problem). Can I just use a universal harness or do I need something specific?

You need the wiring adapter that you hardwire into your factory harness. It allows your separate turn signal system to work with any standard trailer wiring setup. They run 30 to 35 dollars. If you are electrical savvy you can do the same setup with 3 dollars worth of diodes! Do a google search for info on using them.

Canadian Tire had some of these on clearance but they were listed as suitable for Chev/GMC - will one of those work or do I at least need one for a dodge?

Thats the one you want, should have 4 wires on input side and 3 wires on output side. It might have a 4th wire for ground, how much is it?

Clearence ones were about $30 (vs $60 for the kit for 91+ XJ's).

Thanks for your help - I'll swing by there later & pick one of those up.

A word of advice, wrap it in foam to isolate it from vibration and do the wiring by pulling your drivers side taillight, plenty of room there for it. They die quick if not insulated!

Good to know, thanks again.