Air Bag Tank Size ?

[roofingbloke]

Im in the UK and just about to order my air bag components, however im getting lots of different opinions on tank and compressor size,

1963 C10, Long Fleet,
Small c notch out back, 2" drop spindles up front,
I dont need the air system to go up & down fast, Just need to get her a bit lower when stationary,

I had a 48 Ford with mustang 2 front end with air ride tec bags, 1 gallon tank, small compressor, all worked fine, 2-3 mins to refill tank.

I was thinking the following, 4 X 6" bags, 1 x 3 gallon tank,

thanks