The Factory aam shaft is pretty good... it's good for 6500 and should be able to handle 10k ft lb before it breaks...
Doing the math at it's majority of tube size which is 6" that shaft should be good to more than 6500 and 10k ft lbs, but im lowering the figure for the swedge section.
If it was 6" straight thru it would be good to 7200 and 12.5k ft lbs
Most trucks shouldn't have a problem with them if they're making 800hp...
Getting it to the ground without bouncing the aam shaft should live with more than 900hp, but at that range and bouncing it will be a different story