Bear in mind that you'll be altering the effective leverage of the axle wishbone/swing arms by moving the spring closer to the swing arm pivot while the axle stays the same difference from it, and may need a slightly heavier spring or a helper spring/rubber bag or something, since the A body...
I used 3/8" X 1" mild steel bar and 1/2" black iron plumbing pipe. The frame was 3/8" thick 3" angle 4" long with 3/8" X 3" X 4" flat welded to make a channel. Cut the pipe to length (3") to bridge channel but first rip a 1/4" -3/8" section lengthwise out of the pipe for diameter reduction to...