[bagged78]

Ok,
1)1/2 ton leafs will work as long as they are the same legnth from mount to mount.
2)Not sure about stock hight for a 58, but the rear is usually 2" taller than the front, so if you want level then a 3-5 would be good, unless you want to notch your frame..
3) no you don't usually have to notch your frame with just a flip kit, but your truck is probly going to be different then most others, your best bet is to measure the distance from your axle to your frame, that could give you a good guess on how much room you have to work with.... On the 73-87 trucks it is about 5" before you start to think about notching the frame..
Hope this helps.. Have fun.