Help with overlooked rear end swap item...

[Wildmani]

So I finished swapping the rear end in my '79 LeMans to one from an '87 Monte SS and overlooked something. Went to put the wheels on and realized that the lug nuts from my old rear didn't have the same threads as the new rear. I'd like to get my wheels on and drop it to the ground to check out the stance from the new rear springs, could someone tell me what "size" lug nuts I'll need to buy. I was planning on going out tomorrow to pick some up, I may as well get chrome nuts while I'm at it, the wheels I have now are the stock steel ones but I'll be upgrading in the future so at least I'll have them. Any help is appreciated! Thanks!

 

[shotgun]

12mm x 1.5

 

[Wildmani]

Thanks!