My street/strip bracket cars 60-s in the high 1.30s and I wanted to keep a oem look.

I built boxes out of smaller 2x2 square stock and welded to frame where shackle mount would of been bolted.

You could easily make a 1 inch spacer vs my 4 inch and weld slider to spacer and already have your "spacer" fabded and drilled to your shackle mount pattern, and bolt them on.

These have worked flawless for 16 years.

Sliders won't be a fix all for your 60 ft. True, but sliders and good double adjustable shocks mounted vertically do a good bit.