Chips,
Delta used long range tanks in the C2 hold of 3 of their L1011-500.
The tanks were made by Marshall in UK and approved by Delta under an EO.
The tanks were of course removable but the plumbing stayed in the aircraft.
Assuming you need these for the Venetian -500 aircraft and 411 has the tanks you will have the following problems
1. Getting approved data especiallly under SFAR 88
2. Finding the plumbing to Tee into the Aircraft system.
Good luck !
