As far as making a new frame, that's probably going to be more work, but the advantage is that you can position the rails exactly where you want for whatever engine, drivetrain, and suspension systems you want to use. The standard size for most aftermarket truck frames is 2x6 inches. In certain situations 2x4 tubing might work near the ends of the chassis, but 2x3 simply isn't up to snuff.
Of course you want your frame modifications to be completely safe, since any failure of the frame, or the suspension clip you're adding can have severe consequences, and cause the driver to lose control of the vehicle, endangering anybody in harm's way!
You can email your questions to Professor Hammer at email@example.com, or mail to Professor Hammer, c/o CLASSIC TRUCKS Magazine, 1733 Alton Pkwy. #100, Irvine, CA 92606. You'll receive a personal reply! We'll print your name and city unless you request otherwise. Ron Covell has made many DVDs on metalworking processes, and he offers an ongoing series of workshops across the nation covering all aspects of metalworking. Check them out online at www.covell.biz, or call for a current schedule of workshops and their free catalog of DVDs. Phone 800-747-4631, or 831-768-0705. You can send a request by mail to: Covell Creative Metalworking, 106 Airport Blvd. #105, Freedom, CA 95019.