Lug nut question, and a different tire size question (I think)

[Bombdigitty]

Picked up a spare set of rims on the weekend. Planning on using them for snow tires for my 2500 bighorn. They are OEM steel wheels with the chrome caps and plastic center caps that clip onto the lug nuts.
pictures below for reference.

The rims are 17". I confirmed they do fit on my truck. Some said they wouldn't fit.

Question 1 - What lug nut do i need for the clip on center caps?

I'm trying to figure out what size snow tire to shop for. My factory size is 275 70R18

Question 2 - looking for opinions on snow tire size. tire calculator says 275 70R17 is close. Only off by 3%.
I believe the DRW 3500's run a 245 80R17. Off by 2.4%, so a bit closer and a bit narrower.

 

[Bombdigitty]

Update,
Another option might be a 285 70R17
This size seems to be more common among snow tires then the other sizes I listed.

And diameter is only 1.5% off

 

[H3LZSN1P3R]

You would have to get the nuts from ram they are just an open nut

 

[Bombdigitty]

You would have to get the nuts from ram they are just an open nut

Are they the zinc coated open steel nuts with the really deep flange?
like this?

 

[AH const]

I have same wheels you need open end nuts.

 

[AH const]

Go on eBay I found a full set of oem take off nuts on there for $30. Put them on some bighorn take offs I bought.

 

[H3LZSN1P3R]

Are they the zinc coated open steel nuts with the really deep flange?
like this?

Yup thats them