Like ctubutis said.
My 1986 is 8800 GVWR, so no converter. I believe it was 85lebaron that said 1987 was the last year with no converters.
The engine emissions label will say Catalyst or Non-Catalyst.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona