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like Stephen said
I would think about getting your orig tank modified,
find an efi intank pump that will fit if yours doesn't have one,
then get someone to weld in a swirl pot inside where the pump will sit
and they can even make plates that flip to let fuel in but not out
this way it might cost a touch more for fab work but u have less stuff outside the car

running 2 pumps and a surge tank adds about 6 or 8 extra hose connections which if done properly is fine but I like to make things less complicated and less chance of problems down the track

go visit some good fab shops who do this often and tell them what u want to do to the tank and se what they suggest

if you have limited room and low cars running a surge tank and 2 pumps can be a pain
as like others have said external efi pumps don't such to good as they like to push better
so if its mounted to high then u get the fuel cavitating and also starving and also the fuel pump can make rattling noises