does anybody have a solution to connecting the two tanks and using an alternative external fuel pump, maybe like racing type like a Holley Blue Max or even a mechanical. I am going to install a rebuilt long block with carberator to get rid of EFI system. 5.8/351w 1989H code

 

You don't want too connect the tanks; one will decide to fill the other, and it will come out the filler neck.

Older trucks had low pressure pumps in the tanks, and a high pressure pump on the frame. Newer trucks have high pressure pumps in the tanks. I don't know the specific years. If yours is older the pumps may already operate at the pressure you need. A regulator can be used for the high pressure pumps.