Pete And Jakes Front Axle. There is a great section in their catalog (at least in mine from the 90's) that addresses front suspension choices,. In fact, he entire chassis has been color matched to the body, he frame is fully boxed, nd all the welds are smooth, he mark of expert craftsmen at.

It uses a chrome posis spring as well. The axle obviously travels in an arc about the front of the torque tube, as the axle and tube are a single assembly with no universal joint between them, which necessitates pivoting mounts between. Don't let anyone charge you $350 for a vega box since these are the same size.
Get hold of a pete and jakes catalog.
Pete & jakes superbell front ends. These were common on early novas and other small gm cars. Pete and jakes' forged dropped. It is easily adapted to other cars and is ideal for your rat rod project.