On my 32/36

1 - is blocked off
2 - fuel goes in
3 - is taken out (going to atmosphere)
4 - is vacuum adv for dizzy

I didn't use the existing fuel rail that runs around the front of the rocker cover. Mainly because the outlet of the fuel rail is much smaller than the inlet of the Weber. Instead a rail a fuel hose around the back of the engine against the firewall. Nice and tidy like.

Carby was tuned for an A15 but works well on my setup, GX head, oval port etc etc.

Some pics they may help you...