You are looking for a 67-72 a-body front bar, correct?

The 66-69 b-body bar is very close and just about 1" wider overall. End link bushing could be tweaked in lemons fashion to fit.

Do you have away bar tabs on your LCA's? If not you could fit a narrower bar eyelet to eyelet if the other dimensions worked. The aftermarket Hotchkis bar is like that. You'd loose rate, but that could be made up by a thicker bar.