Blazer runs then dies

You have done all the right things I would have thought of. Might be a relay heating up and cutting out. The most likely one would be the fuel pump relay. A failing camshaft sensor should set a code like P0340. Maybe it won't.

Yeah I don't get it I'm good with truck but I don't know what to do if I'm not mistaking I f I changed that awhile ago to

Don't give up. It's usually something really minor that drives us nuts. New fuel pump malfunctioning, loose ground wire to engine, loose connector to pump. When it stalls, try to determine if the fuel stopped or was it the spark. Good Luck.

How would I go about check to see if it stopped

Soon as it stops, try cranking it back up and test for fuel pressure and also check for spark. If you find one missing, it will narrow down your search. Either it's lack of fuel or spark that makes it stall.

It we'll not start tell it cools all the way down