I just recently started having a problem with my 4.3L where it starts
fine but then it dies after about 30 seconds. It will start right back
up and do the same thing again and again. I just replaced the fuel pump
and have checked the fuel filter. It seems like an electrical issue.
Can anyone help?

I had the same issue with my starboard engine. After doing some visual and hearing checks I noticed that I was getting an arc from the coil. I switched wires from starboard to port and the problem didn't follow. I switched the coils from one side to the other and the problem DID follow. After buying a new coil, the issue went away.
Hope this helps!