Something like this. You have to remember that Reagan had a reputation as being pretty radical at this point; he was sometimes called "The Western Wallace". In addition, Reagan at this time had a persona which was quite angry, as opposed to the sunny optimism of his actual presidency. Another thing is that obviously, in 1968, the country wasn't nearly as desperate for change as it was for 1980 (hence the in my view correct consensus people on this board have that getting Reagan elected before 1980 is an uphill battle).
I will note one thing though: There was talk in 1968 of a Rockefeller-Reagan unity pact at the RNC to stop Nixon. I'm just going off memory here but as I recall they did actually try to do that but they couldn't agree over who would be on the top of the ticket. If you can get Rockefeller to agree to be Reagan's VP, the election gets a lot more interesting. Maybe Reagan doesn't win outright, but he might get the election thrown to the House (even in the map I have above, flipping just NY is enough to stop a majority for Humphrey).
