Somewhere, years ago (I think) on this forum, a guy converted his '86-on car to 7" rounds. Whether this or your goal of quad headlights, it doesn't matter. The important thing is that he retained his '86-on turn signal lamps, so they fit in the fender perfectly.

What he did was fasten the '86-on turn signals to the fender using flat iron pieces, running vertically, as a mount. You would have to cut/grind off the mounting extrusions that fasten your turn signal lamps to your current headlights. Leaving a flat inboard side, this would be bolted to those flat pieces. He ran bolts through the lamp housing and the flat metal pieces, and they were solidly in place on the fender. Then he mounted the headlights without any concern about the turn signal lamps.

It seemed very easy, from the pictures he posted.