Sandy - That Tapping jig is very neat - I never knew of their existance!
RE: Fuel return line / pickup line / fuel level sender - I would make sure that you have the fuel return line sent off in a direction away from the pickup and sending unit. I've found that with high volume pumps, they have a tendancy to promote cavitation near the pickup. Also I would encourage you to consider a Duck-Foot fuel pickup similar to this one:
ATL Fuel cells - Pickups and Fittings Part No. TF239
Nice work!!