Sorry you didn't check for opinions first, but that's water under the bridge now.

Personal opinion here, others may differ. I've never been fond of the clunky look of the FM crossmember stuff. More substantively, if yours is like the ones I've seen in the past I don't like the smaller frame contact surface of the lower crossmember section. I have a strong affinity for Heidt's stuff, and like the way it wraps fully up the inside of the frame rails to the upper suspension "hats". I think it reinforces the chassis better as well as having a better "look". The upper shock mounts on a Heidts are a nice conical shape, the FM looks like a piece of pipe with a washer welded on. Probably not much difference structurally, but again, the Heidt's appears to be more professional.

If you've got any concerns about whether or not what you've read about the construction quality being diminished it would be a good idea to take the pieces to someone with equipment to check for cracks, week welds, etc. Suspect welds can be redone as long as the adjoining metal is intact.