fuel upgrade questions

[MILD67]

i have decided to take the mussy off the road for the winter and do a few things to her.
with the fuel system at the moment its got a later model tank for more klms out of tank and 3/8 pick up instead of 5/16, im still running 5/16 line to the mechanical H/V holley pump, then 3/8 to a 700 holley DP.
i have purchased a holley electic pump and regulator, and have been told to put a outlet at the bottom of the tank. true? if so, can i use the drain plug?
should i run 3/8 lines or go 1/2?
do i need a return line? if so, do i use the old lines?
the pump has 2 oulets and 1 inlet, why 2 outlets?
the reg olso has 2 outlets and 1 inlet, why?

[BLKPNY]

The 3/8 will be sufficient, the 1/2 will be plenty. Your system is as small as the smallest area, so you could have a tight bend in the 3/8 line, and it will be as small at 5/16 anyway. At least, if you have a tight bend in the 1/2", it should still be as good as the 3/8... If you get what I mean?
Check your fittings too, I have some -6 fittings, that have a tiny hole in them, for the flow.... The fitting is a restriction.

Getting a sump put on your tank will cost $150 - $200, so no big deal. Any fitting size you want, front or rear of the tank.

The old Holley blues I remember, only had 1 outlet? But newer, bigger pumps have a return from the pump, back to the tank, perhaps that is one of the outlets you are looking at?

The regs have 2 outlets, so you can either just use 1 line to the fuel log, or use the reg in the middle of the 2 bowls, and use the reg as the t piece, feeding both bowls.

[MILD67]

so block off 1 outlat on the reg?
can i use the  standard 3/8 pick up or should i get a new one at the bottom?
the tank has a sump plug, can i use that?

[BLKPNY]

Get the regulator mounting plate that mounts the reg next to the carby, and run 1 line from each side of the reg, to each bowl.

You should be ok with the pickup in the tank, and 3/8 line front to rear. Fit a fuel pressure reg, and you'll see if it isn't enough.

[MILD67]

should i use hard line from tank to engine bay or will braided hose surfice?
is it best to mount pump as close to tank and as low as possible?
and the reg as close to carby as possible?

[6T9rustang]

should i use hard line from tank to engine bay or will braided hose surfice?
is it best to mount pump as close to tank and as low as possible?
and the reg as close to carby as possible?

Not sure if flexible fuel line is legal for the length of the car. Aluminium fuel line would be much lighter...

Most electric fuel pumps like to push rather than suck so yes lower and closer to tank equals longer pump life.
Regulator should be mounted as close as possible to the carby because thats where you get the biggest pressure drop so you want the regulation there. More accurate.

[6T9rustang]

.....3/8 pick up instead of 5/16, im still running 5/16 line to the mechanical H/V holley pump, then 3/8 to a 700 holley DP.

After having another read I've also discovered another issue there. Fuel pick-ups or suction side of pumps should be larger than the pressure or discharge side always.  Your 3/8 pick-up is a good move but the 5/16 line to the pump defeats the good move. You should have a 3/8 or larger from the tank to the pump.