1974 Fuel lines, size and number????

[kanuck]

As I am pretty much putting a 1974 truck together, (1974 cab and front end, 73-80 frame and parts from where ever), I was wondering what I need for fuel lines.
I kept a set from a 1984 short box I disassembled for a pattern to bend my new ones, but it has 3 lines running back towards the tank. Two seem to go from the mechanical fuel pump back to the tank, (one 3/8 and one a bit smaller) and another one from the drivers side rad. support back, (charcoal canister??).
If I am building this with plans for a strong 400 to 500 HP engine, (still contemplating small block verses big block), what fuel lines will I need as I have no pollution inspection and I am not worried about a stock rebuild.
Planning to keep a mechanical fuel pump, unless I run into problems with that idea.
Have bought a fresh gas tank and am running it on the passenger side, but am reusing the old float and sender unit that I removed from a 1980 short stepside.
Thanks for any info you can give me.
Hagen

Frame being assembled


Cab being prep for re-assembly with frame. Only rough spot is inside rockers