4/5 drop kit for Suburban...

1989 suburban 2500, does anyone know where I can get a 4"/5" drop kit for it? I know I can get the front with springs and spindles, the big issue I'm having is in the rear. All I've been able to find is shackles for a 2" drop, no luck on a flip kit, can anyone help? It has a 454 and 8 lugs all the way around if that helps at all.

BUMP for some help on this!!