Need help!

[slammed95]

Ok I have a new truck that I bought with the drop on it, I wanna go lower and put a 20 inch factory gm wheel, I wanna at least have a 5/7 drop done, it's got bell tech notch and shackles on front and rear of the leaf spring, It's got just a spring on the front I think, I'm not sure how low it is I was thinking like a 3/4?? But I was gunna put a 3 inch drop leaf on the back and put a drop spring and spindle in front, like I said I want a total of 5/7, if anyone has an idea how low it is let me kno, also what would be the best tire size for a 20 inch gm Texas style wheel, I was thinking a 245/35-20 but if someone thinks a differnt size would be better let me kno, here's a pic of my truck and the wheel I wanna use
http://i1003.photobucket.com/albums/af152/slammedmx/1185b7c4.jpg
http://i1003.photobucket.com/albums/af152/slammedmx/e610cbdd.jpg