The initially wildcat .338/06. later legitimised and the .338 Win Mag were "copies" of the .318 WR. In Europe they copied these with the 8.5x63, essentially another .338/06 I believe. I assume it is the same case head?

If I lived in the USA or Canada, I would definitely have a .338/06.

I did consider a 8.5x63 barrel for my Mauser M03, but at $2500 for just a barrel .... and close to my 8x68S anyway. Since then Mauser has ffffed up its line up with "rationalisation" and Blaser has downgraded the choices at its group company. So little options now available. Cheaper rifles, lesser ranges. Killing off a brand.