Here are some pictures of the bolt-on X-brace frame connector I fabricated from 1x2 box heavy gauge steel.

I welded 4 seperate 1/4 inch steel plates onto the subframe points of my vehicle and then drilled two 7/16" holes in each plate for bolts to allow easy removal of the frame connecter in order to service driveline components.

The addition of this piece stiffened the chassis substantially compared to stock.  Only minor clearancing of the exhaust was required to prevent it from contacting the brace.  All this for the cost of the steel, which was under $30.