Here is a fuel sender at the end of one of the tanks.
On the inboard tanks the senders are on the in board end.
On the outboard tanks the senders are on the outboard end.
I left the sender bracket arms full length and put the
sending unit all the way at the end on the outboard tanks.
On the inboard tanks I made them as short as I could.
This was an attempt at getting as close to the low end
of the tanks as possible.
I've tried to bend the float arms so that they meassure
correct when fuel is low. For the most part the float is
going to hit the top of the tank and never measure full.
There's a trade off between getting the float arms short
and keeping them long enough to produce the force to move
up and down by gravity.
In this picture you can also see where the auxilary tank
pass through is screwed into the end of the tank and sealed
with pro-seal.
The screw flange for the pass through tubes is an aluminum
clamp type collar purchased from McMaster Carr.
This picture also has a clear shot of the air valve I
purchased to hold the air in the tank.
I found these at Lowe's