What kind of temps can a stock motor handle?

1300 - 1400 is OK. 1600 or more is dangerous territory without beefy upgrades.

Some get way higher. All depends on the truck and load situation, tuning, condition of internals, etc.

If I remember when my truck was stock, my egt's would not get near 1000 pulling backhoes, trailers full of concrete and plaster, job debris and crap.

1375 max sustained under load is what GM says. Obviously higher temps can be seen, but only for a very short time. Say <30 seconds...

I have an 05 with super chip set at tow/performance and 4in mrbp exhaust turbo back. Just put egt guage in and was suprised how high it got. Not pulling anything, foot to the floor it got up to around 1300 quick but stopped there.