Greg,
Life hasn't been very forgiving lately, but I finally have your tank calcs completed, overall and by inches.
Your tank came in at 53.4 gallons overall using the outside dimensions. Accounting for the volume of the aluminum, should give you 51.0 gallons inside volume. Due to the nature of the tank design and the sender design, when you reach 'E', you will have about 5 qts of fuel left.
Sorry for the delay.
Bob