Is a "functional replacement" (same mounting points, same leverage, same diameter) legal? I would think so, since it's no advantage.
Except for chassis clearance (oil pan, center link, tie rods), the only variables for the bar itself are:
1. diameter.
2. width across the arms (should be close to the width across the lower shock mount, etc.).
3. arm length, from center to link, you can lengthen the arms with a sleeve or cut them off.
Some more modern car has to be pretty close, the center width has to be pretty close (within a few inches).
The link brackets look like shock mounts, attach anywhere with a clear path. The links are fairly generic.
The center brackets generally go under the front radiator support or cross-member, with the arms pointing back (doesn't have to be right under the axle center), they're just big U clamps with bushings.
Just a guess: 1" OD has to be safe, and a big improvement over none at all. Each 1/16" can be felt, 1-1/8" is a huge change. 1-1/4" may be too big.
Once you find a suitable donor car, there are probably at least 2 different sizes used for wagon, performance etc., common flea market cleaning-out-the-garage $10. item.
