Where can I find standard thread wheel nuts for earlier rims?

[67GMCcampercruiser]

I was planning on putting 90's style rims on my 3/4 ton 67. The rims came with the special nuts with threads on the outside which you then screw the plastic nuts on to hold the center cap on. The nuts that came with the rims are metric and a little loose on the studs which I'm sure will strip the threads. Anyone sell nuts like this but standard thread? Thanks