240 Front Bumper Bolts

In the process of converting my 280 bumpers to 72 240z style. Working on the front one right now.

Does anyone know the correct size for the secret little bolt that threads into the bumper ends (thru the body below the headlight area)

I did a search on bumper bolts and someone claimed they are 6 x 1.0 , bought 2 stainless ones, they do not thread in, feels like the thread is wrong.

Are they special tapered bolts or just standard?

If anyone knows or can verify the correct bolt size, let me know....

My car looks different with no bumper