The way it was described to me from a guy who has done about 10 of these. (He is going to be doing a 79 Camaro front clip in mine soon) Unless you are planning on doing some serious horsepower upgrades (like something real sick like a 572 or something) and doing some real serious ragging on it (drag racing/serious holeshots) there really is not any need to box the frame. Its just extra weight, and creates that much more potential for heat/stress damage from all of the welding.
