newbie here, need lowering help

[Gixxerboy]

hey everyone,
I am new to the scene and have got my grandpa's truck given to me, a 1970 GMC.

as of right now it's all stock and I have been looking into lowering it.

I was thinking just plain springs, and spindles to get around 5 inches, but it's just not enough.

If I buy a air ride kit and install it, just the way it comes

1)how many inches can it lower my truck??

2)what all would be needed to make the body touch the ground??

3)what is C-notch?

4)what is a four link setup supposed to accomplish? is it needed?

5)body drop required?

I am new to the truck scene, and the air ride setups, please help, and help is appreciated.

thanks again
James