Lowering block question?

[LGCC10]

I need help with the size of the lowering block I should use. I will be installing 2 1/2 drop spindles with air bags in the front. In the rear I have put a large c notch and will also be using bags with the original trailing arms. How do you know what size block to use? I would like for the truck to lay as low as possible with this set up. If it makes a difference I plan on using firestone bags. 2600's in front,2500's in the rear.

Thanks for the help,

Pete
67 chevy stepside

[lost wages]

3 inch block with the right step notch will lat the driveshaft xmember on the ground before arms hit the frame. Thats with the 2500 bag.

[LGCC10]

My notch is eight inchs, is that big enough? Would that work with the bags in the same spot as the coil springs or should they be relocated. With a block that big does it have to be shimed?