I am not qualified to talk about the harness, but I do know that bulbs from a 91-96 won't work on an 88. Also, whatever bulbs you have for your regular 91-96 headlights won't work with the T84.
T84 use an H4 bulb I believe, and regular late model B-Body are 9004? Anyway you may or may not know that you also will have to change the conectors on you wire harness to wprk with the T84 also. I hacked mine up putting my T84 on , and wish I would have just bought someones harness.
The factory part T84s came with H4 bulbs in them, and I have used them for a few years now and they work great for me.