This is fairly common on 78 and newer trucks with the cable clutch. 77 and older pivot at a different point due to the hydro clutch master cylinder. I've yet to have any trouble with any of the older hydro clutch brackets. Here are a couple of old posts regarding this:
http://forums.luvtruck.com/viewtopic.php?t=6274
http://forums.luvtruck.com/viewtopic.php?t=3636
http://forums.luvtruck.com/viewtopic.php?t=2537
I was able to take the bracket out through the hole the gauges sit in. Once you have it out you'll need access to a welder to fix it up. I recommend adding some gusseting to strengthen it up. If yours is too far gone you could pull one from a junkyard truck. Just make sure you get one from the right vintage of truck. 72-77 are the same, and 78-80 are the same. If you want a new one, here are part numbers, if a GM or Isuzu dealer can still find them:
94022556 series 2-6 (1973-1977)
94027039 series 8-10 (1978-1980)
A new bracket for series 8-10 is still going to fail eventually. I'd weld extra support on a brand new one if it was going in my truck.