I did an EFI conversion on my '65 3/4 ton some years back.
Since I was using a Holley ProJection 650 CFI 2bbl TBI kit, it didn't need a lot on the inlet side so I was able to use the stock pickup line. However it did need a larger return line to prevent excessive back pressure which messes with your pressure regulators working pressure.
I used stainless hardline for bolth supply & return lines and used rubber lined adel clamps to mount them to the frame rail with short sections of fuel hose to connet them (I cheated & used an aircraft shop to make the pressure lines using AN fittings, looked very sharp & no leaks!). You'll want a good high flow FI fuel filter between the tank & the pump as well, thankfully the Holley kit came with all of that.
As far as modifying the tank, I took the tank out, rinsed it a few times, aired it out, Then I used another piece of stainless line bent to run up one side of the tank and into the top in a sharp J shape, drilling a hole at the top for it to run into the tank. Then I took it to a radiator shop to have them braze the return line onto the tanks seam and check it all for leaks. To aleviate the whole explosion hazzard they submerge the tank and only expose the area they need to work on.
This is also a good time to have the tank cleaned & coated inside if you dont need a new one outright.
I brought the tank back, figgured where the return line would pass through the floor and drilled an oversized hole so I could instal a rubber grommet and then boted it back in place.
Worked good for the rest of the time I owned the truck.
1956 GMC 370 dump " 'Tater "1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI
I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P