That is definitely aftermarket.
Kind of looks like the antenna from a newer Ford pickup. But it could be almost anything with a front cowl mounted antenna.
'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...