Does anyone have any ideas on mounting an elec. fuel pump in the trunk?

Sounds like you want to live dangerously. I recommend mounting it under the car in front of the fuel tank. Attach it to the floor inside the rear end cavity. It fits nicely and it is much safer.

I don't have a fuel tank in the usual spot . I removed it and put a fuel cell in the trunk.

Since they're designed to push fuel and not pull it, just make sure it's below the pickup level. That way at least it will gravity feed as far as the pump.