Very intriguing that you would ask this question, most people who are interested in converting the headlights look into the Re-Amemiya FC2000 headlight conversion or a clone of that bumper type, it gives room to upgrade the rx7 factory headlights to projectors. I'm personally completing this conversion on my fc right now, and I'm going to use hella bulbs for the replacement headlights with custom mounting brackets.
www.rallylights.com sells some suitable replacements for this. The other option is to switch out to Chaser aerokits carbon fc hadlight buckets that replace the factory flips.