i replaced my gas tank, original was leaking. now the engine starts and runs good, but after driving a few miles under demand it stalls and starves of fuel. i have to give it a few minutes pump and crank a while and it will run good untill it starves of gass again.

 

You didnt say which fuel system you have...(TPI, carb, TBI...) I'm gonna take a stab and say you have a fuel inj setup. Did you also replace the sending unit/fuel pump setup? There is a rubber hose on the sender that attaches the fuel pump to the hard line. If this is broken/cracked it will not allow fuel pressure to build and will starve the injectors.
When you first turn the key on (One click before "crank" position) You should hear the fuel pump "Prime" after a second or two this should go quiet. If it does not then you have a pressure problem.
Let us know.

 

Was there a baffle in the new tank?

 

yes there was a baffle and it is carburated with mech fuel pump