Sorry to be asking this seemingly simple question but I have an 03 dualie 4X4 and want to get rid of the simulators and powdercoat the wheels and just use centercaps and long big rig style lugs, I think I have it down to 9/16 X 18 size and bulge seat acorn caps, am I even close? this has been a tough search.

 

that's what my aftermarket lug nuts say on the side, 9/16 x 18

just get the "long" version, and you will be fine.

the "rent to own" furniture stores that do rims, have more lugs/lock lugs in stock than any tire or parts store.

i got lock lugs from there for $19, they are $35 from a dealer