I change this fuel sending unitAnd for some reason it doesn't want to start it starts but then it stalls out what's wrong with it

Sounds like a fault with the installation process or the parts used. This is not a vehicle i'd mess around with outside of a high end repair shop with an experienced technician. There are many possible causes, such as a mis-fit fuel line, wiring connector, aeration of the fuel system -- too much to guess at. Seek professional help. www.repairpal.com/repair-shops