Replace the cowl seal. Its between the windshield frame and the top of the cowl. If you laid the windshield forward to do the lights or run the wiring then you disturbed the seal.
Or it could just be a coincidence that the leak started after you mounted the lights. But the cowl seal is what the problem is. Only thing it can be.
'87 YJ, 4.2L built and bored, 8.5" of lift, 8.8 rear, AX15/NP 231, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...