Black and red is a positive signal from the original relay to the fuel pump, BROWN is earth, on fords of this age BLACK is always a switched live.
On the new relay, 30(or 30/51) is battery input through fuse by battery, 87 is output to pump, 85 and 86 are earth and live(trigger) from existing fuel pump live wire.
85 and 86 can be reversed doesn't matter still works perfect.
I found just behind the rear seat upright metalwork there is a 8mm hole, so use a relay holder and relay here, so that when at shows etc you can simply pull the relay out for a bit of added security, make sure the original live is taken after the cut out switch, as this needs to remain in the circuit, you will need to use the existing connections though if on a 044(std) pump just chop about 6" from end and join to new wires.
tabetha