There are a million good reasons to upgrade the suspension on any classic truck, but especially those equipped with a straight-axle, parallel-leaf frontend. These suspension designs are archaic at best, given today's technology and high-demand driving conditions. As a farm hauler, the parallel leaves and straightaxle suspension designs work great for hauling heavy loads or traversing rough, uneven terrain; but as an urban cruiser, the straight-axle design leaves a bit to be desired. The ride can be rather rough, the stock steering a bit of bear to handle, and the brakes slightly unruly. Put short, there are a number of desirable upgrades to be had.
This upgrade scenario came up in conversation recently when it was time to deal with the stock suspension under my newly acquired '52 F-1 project. The stock front suspension was intact, but someone had done a rather crude de-arch job on the springs, resulting in a frame on axle ride height. It looked nice and low, but there no way it was going to ride at that height. The springs would have to be replaced, but the question was, "With what?" I could swap in a pair of new springs, perhaps a reversed eye set, along with a dropped axle, but I'd still be stuck with that old ill-handling stock suspension. I weighed my options and decided that the easiest way to cure my suspension woes was to install an entirely new front suspension kit from Heidt's Hot Rod Shop.
The Heidt's kit we're using is based on the old standby Mustang II design, upgraded with Heidt's tubular A-arms that alleviate the need to run the stock style strut arms. This upgrades that old straight-axle suspension system right off the bat to a modern independent setup, gaining a huge step in performance. The kit comes with a new crossmember that will locate the lower A-arms, and two spring towers that locate the upper A-arms, as well as the coil springs and shocks. A power rack-and-pinion unit that also mounts off the new crossmember will replace the stock steering box. GM calipers and 11-inch Ford rotors complete the upgrade by replacing the old Ford drum brakes with modern disc units.
Along with the upgrades to the front suspension, our F-1 project is going to get new drivetrain components in the shape of an early Chrysler Hemi backed by a T-5 trans. Out back, a new 9-inch Ford rear will replace the stock unit and new suspension components will also be installed. Once complete, the chassis will be finished in Chassis Black and will be upgraded and capable of handling anything the modern highway can throw at her.
As shown in the lead photo, the first step is to remove all the stock suspension components, spring shackles, and shock mounts. The front crossmember is about the only stock component left intact. | 
The next step is to box the framerails. The `rails should be squared up as far as the flanges are concerned, and made straight and true. The boxing plates are then clamped in place against the `rails. The bottom flange of the frame rail is slightly wider than the top as well as having a flared shaped to it. Using a scribe, the bottom flange is marked and trimmed to better match the top flange. | 
Once satisfied with the fitting of each boxing plate, they are then welded to each rail. Short, 1-2 inch welds are used alternating the location to avoid excessive heating of any one area and warping the framerail. The welds are then ground smooth. |