Sam Yorty wouldn't have been an acceptable pick for Eugene McCarthy, even if as some sort of sop to conservative Democrats; he regularly criticized followers of the Civil Rights Movement, publicly feuded with other big players in the California Democratic Party such as Jesse Unruh (and his selection would be considered a slap in the face to those same people), and additionally was a Pro-War Democrat, the anti-thesis of the entire McCarthy campaign. The closest comparision I can think of is the '24 Democratic ticket of Davis and Bryan, who similarly managed to alienate their respective constituencies by seeming influenced by the other.
Of course Rockefeller wouldn't be doing himself any favors by nominating Daniel Evans, essentially daring conservative Republicans to not vote for him in November, and a good number might indeed defect to the Wallace campaign or not vote at all; certainly the South as a whole, the Old Confederacy and maybe Oklahoma, could be written off.
However beyond there I think Rockefeller would win comfortably, the Democratic ticket not capable of creating a coherent message, and Wallace not being competitive outside the South, Industrial Midwest, and maybe some parts of the Prairies.
Rockefeller might pick a California Conservative, but it would have to be a Representative or Senator. Evans constantly aligned himself to the Reagan base while being on the issues a Rockefeller Republican.
