Could I make custom radius arms for cheap or is it better to buy them?
They have these from James Duff
Ours are the only Early Bronco Radius Arms to utilize 2" diameter, 1/4" thick heavy wall tubing, cast iron head units, and massive 1" bore high quality Rod Ends for maximum strength. Arms are designed with built in caster, offset to clear larger tires and tight to the frame rail to improve ground clearance. 10 3/4" longer than stock—Moving the pivot point farther back vastly improving suspension travel and articulation, overall handling and control for on road driving. Built in lower shock mounts for use with stock shock mounting position or our Stage 2 Hoops and our Long Travel Shocks for 15" of travel. Best results are achieved when these arms are used in conjunction with Duff suspension components. Blue powdercoated for long lasting good looks. Requires reuse of original C-caps. Includes arms, head units, rod ends, bushings and all necessary mounting hardware. All new parts, no core necessary.
#5350 Stage 3 Tubular Radius Arms, 1966-77 Bronco, $699.00
But then how do I go about mounting them to the frame?