I've crunched the numbers before and I recall the GMC transfer being good for over 30,000 ft lbs of input torque. It sees around 34,000 with the Hydramatic when shifted into low reverse. Beefy indeed.
Montanatower, if your making an offroad wrecker chances are your keeping 6x6 capability, which means your original transfer is staying put. The "ears" breaking off the hand brake support is very common, mine were broken and mig welded back on at some point in it's life. Last I checked, you can buy a new brake band support from Alfa heaven for $100. I would attempt repair only with the unit taken off the back of the transfer, it is cast iron and must be pre heated and then buried in sand to slow cool after welding.
The GMC handbrake is for flat ground only. It will not hold reliably on any kind of incline. So you might as well do without, wheel chocks, flat ground or not is IMO the only safe way to keep a Jimmy where you parked it. I recall a story posted by a small town fireman, their M211 was parked on a hill with the handbrake on out in the forest on call, without warning it began rolling and chopped down 7 tall poplar trees at bumper height.