offset for wheels

[RChevy.48]

What would be a good offset for a set of 18" wheels? I want to lower my truck 2/4, and maybe go 4/6 in the future. I will someday be looking for wheels on ebay and want to know what offset to look and ask for.

Thanks,
Randy

[99 red silver]

My wheels are 18X8 offset 19, backside 5.25, bolt circle 6x5.5. I have 2/4 drop.

[farmtruc]

http://www.ls1truck.com/members/99redsilver.html