Bolt-In or Weld-In?
Total Cost Involved markets this kit as a bolt-in assembly but a few of its parts—specifically the upper-arm mounts and spring cups—weld in place. It’s a bit misleading but there are legitimate reasons for both installation methods and it has to do with the frame design, not convenience.
Chevrolet employed what many call top-hat frame construction from the late ’30s to 1954. The thinner-gauge top and sides of each framerail form a C-channel of sorts that flares out at the base. Riveted to those flanges are heavier-gauge steel strips. What emerges is a boxed frame section that’s stronger than a conventional C-channel, a property that let Chevrolet build relatively strong frames without having to resort to excessively thick materials or bulky crossmembers.
But the design imposes some unique requirements. The frame flange prevents the crossmember from wrapping around the framerails, a requirement for a suitable weld-in installation. Furthermore, to weld it to the chassis would mean attaching it to the bottom plate and along the very edges of the flange, neither of which is very strong.
Instead, Total Cost Involved designed this one to bolt to the frame flanges. The bolts approximate the rivets that Chevrolet used in the sense that they capture both layers where they’re strongest: along the centers of the flanges. That Chevrolet attached pretty much all structural components to those flanges indicates that it’s likely the best method for the application. It’s not impossible to approach or even exceed the same structural integrity with welding but it would require considerably more work to weld the crossmember to both layers of each framerail.