Lowering a 71 longhorn 3/4?

[Thayer03]

So I have a 71 GMC Longhorn 3/4 ton. It has the 8 bolt pattern wheels with extremely large leafs in the rear.
I want to lower it just enough that when I put a set of 18's and nice rubber it can still fill out the wheel wells. I want to keep the 8 bolts and some of the heftyness to it but want it to be lower.
Any good suggestions on this? can I just go get a new set or rear leafs made to lower the back and new front coils?

I am used to lifting vehicles being a former jeep owner so this whole lowering thing is new to me!

Thanks

Randy