While it is true the alumimum versions are a little on the light side for anything but the lightest cars (maybe 1500 pounds or less), the steel versions are actually quite good. There are only about a bazillion T buckets and other rods running them, and I can't ever remember hearing of one failure. The aluminum ones had the potential of cracking the case on a too heavy car, but guys loved to polish them and use them anyway.
We are running three Flaming River versions of the Corvair reversed box, one in my T, one in my Son Don's T, and one in Dan's 455 Olds powered 30 rpu. Dons and mine have been on the road for over a year and the boxes have been good. Don's is actually too easily steered for my tastes, almost like power steering, and mine is a little stiffer because of the fact I am using some steel bushings along the way and a U joint.
The only reason we went with new vs an original Corvair box is because the originals are getting tougher to find, and the cost is not too far off of a brand new Flaming River.................I just like new parts wherever possible.
Don