I have a 1996 4.9l after it sits over night and i start it up I get to normal temp them it continues to over heat alodt to the end of the guage then drops back to normal temp

 

Sounds like the gauge is messed up. Maybe the temp sending unit or the gauge itself. Or if the engine is doing that then maybe the thermostat is opening late. I would replace it they are a cheap part and are part of preventative maintenance. I've heard they are pretty easy to change on a 4.9. It was kind of a PITA on my 5.0

 

Thermostat is what I was thinking cause the guage is reading proper cause if it's hot outside and I run the ac hard at idle it does overheat

 

Sounds like the culprit. Get a 195° t stat that is the OEM one. Also some permatex water pump & thermostat housing rtv and clean and coat all mating surfaces. Also you'll want to put some on the lip of the t stat and press it onto the housing and let it sit up for a little bit. This will keep it from slipping down in between the housing and intake and causing a huge leak. Oh also make sure not to install it backwards.