Taking off stock shifter arm?

Hey, i got a 87 b2200, 5speed. I just finished makein my shifter arm for it, our of some billet and some hard work. But now i get in my truck to go take the stock arm off, and i cant seem to? does anyone know how to take that off? i dont see a nut at the bottom or nything like a set screw or nothin? i need to take the whole arm out then slide my shifter over the stock rod.

anyone have this problem before.?

heres the shifter for anyone that cares.