The cossie wiring is a bit old now, so any shortfall could have disastrous consequences, best to rewire through relay, easy to do about 2 hours work, there is already a nice hole up behind the rear seat just right for a relay holder, plus as an added measure take relay out at night etc.
This is what I did using the oe wire to trigger relay, so still goes through cut out etc.
Use 28/030 wire as this is more than enough at 17.5 amps continuous, the group a use 13 amps@12 volts.
The std pump is good for around 380 bhp, group a ones will need a connector for the fuel side.
Matt Lewis sells these ebay or 01922 692424.
tabetha