I think the trucks are rated to two 3,500 lb. A class II hitch will bolt into existing frame holes. You will need a 'converter' box to run a flat-4 trailer connector since it has combined run/brake lights, which the truck do not. Just splice into the existing light wires. A wiring diagram is a big help here. Figure $150 for a Class II hitch and $50 for wiring and the box if you install yourself.

1989 4Runner Special Edition
22RE, 5-spd.
TG 3" SAS, MC DuaLs, 4.56s, Air Locker
Hi-Clearance panels by
www.toyotafiberglass.com