intel xeon gold 6268cl for dell precision 7920 tower?

Correction:  Scroll down even further and there's a 3rd list.

So I found a deal on a Platinum 8260! Going for it... what's the most I should pay for it btw? 

You'll have to do your own shopping around on that one.  You didn't say if you were buying new/refurb/used.  Ebay is a great place to find good deals and see what the price range is on many products whether you're buying new/refurb/used.  If buying new, compare prices on Amazon with those on eBay.

Depending on what country you're in, you might have your own versions of those websites or other sites you can check out.  Newegg is another one.

@bradthetechnut​ it was an open box cpu but missed the sale. 
what if I buy the ES version of the 8260/8280? 

I found nothing to support that the ES versions of Xeon CPU's work in a 7920.  While the socket type is the same, supported CPU's are limited by chipset.  I can see why you want to save money though.  8280 & 8260 CPU's ain't cheap.

I also checked out Precision 7920 Userbenchmark.  I didn't find any users using ES CPU's in the 7920.

@bradthetechnut​ thank you very much for your assistance.

how about the 6262? I saw that it was discontinued, but it's going for $200 on eBay. the V version of the same cpu is about $500

and the 6252 $464

my last resort would be the 6238 $360

any recommendations ? I also plan to upgrade the ram from the 2133 to the faster the cpu can support. 

btw, I am in california 

Use the Userbenchmark link gave to see if any the those CPU's you listed are used in the 7920.

If you don't know already, use the owner's manual to link CPU with RAM speed.

From the Precision 7920 Spec Sheet

@bradthetechnut​ I found a few builds with the 6252 so it's settled: Xeon Gold 6252.

thank you very much for your assistance :)

You're welcome.  :)  The Gold 6252 is also listed in the Tech Guide, so it should work.  Good luck with it!!  :)