The Thule 300 Raingutter Complete Roof Rack Base System fits your 1994 Ford Bronco full size version like a glove. It attaches directly to the raingutter rails on the edges of the Ford Bronco roof. You can then attach the surfboard carrier to the load bars. The 65 inch load bars are the recommended length for the 1994 Ford Bronco roof top.
Thule Car Racks - 2008 Thule 300 Complete Car Roof Racks
You should also consider getting a 4 pack of Thule Locks to lock the 300 Raingutter Foot Pack to the Ford Bronco rooftop.
You have a couple of great choices for surfboard racks now. The Thule 554XT surfboard carrier attaches directly to the Thule 300 base rack load bars and can hold up to 2 surfboards. A very easy to use, durable and inexpensive option.
http://www.orsracksdirect.com/thule-554xt.html
Another excellent option is the Inno BoardLocker surfboard rack. The Inno Boardlocker connects directly to the Thule 300 base rack load bars also. The very cool feature about this carrier is that it includes a super easy to use specially integrated lock system to lock your surfboards inside the carrier. Carries up to 2 surfboards too. More expensive though.
Inno Surfboard Racks - 2008 Inno BoardLocker Locking Surfboard Rack & Sailboard Rack