I asked Guy Croft about this, because he supplied it all, and I think he has pretty much answered the question. Here's the reply for anyone else who is thinking about doing this:
Mount the pump on the rubber mounts in the boot, run it off a relay activated by the ignition switch. Use cabling of similar gauge to the cable already fitted to the Facet pump - it does take quite a lot of current. Mount the pump no higher that you have to!
Mount the regulator and gauge adapter in the engine bay, gauge between regulator and carb. Remove the gauge and plug the adapter after calibrating the fuel pressure to 3.5psiwith ignition on but engine not running.
Cheers,
Justin.