What x-member with Wayne due subframe in 67?

[rsimons]

I have a Wayne Due subframe in a 67 Firebird, with an LS3 & T56 magnum trans. What X-member will fit best? The frame rails are 31" wide, similar to the Heidts, but the X-member mounting flanges are welded higher on the frame rails than the Heidts. I may mount the Heidts x-member to the underside of the flanges with spacers but I was wondering if anyone knew of a direct fit solution.