Fighters who consistently had world class sparring?

Muhammad Ali....he sparred with Larry Holmes, Tim Witherspoon..Tony Tubbs ...and Michael Dokes

 

Mike Tyson....he sparred with Greg Page ..Oliver McCall....and there’s some guy on YouTube who is pretty well known as a sparring partner ( forgot his name )

 

And Ingemar Johansson (once) and Jimmy Ellis (for 20 years) and Greg Page and Jimmy Young and Ron Lyle and Jack Bodell and Roy 'Tiger' Williams and Scott Ledoux and Bernardo Mercado and the Russian Olympic team and everyone, really. (LOL)

 

Most guys that have the backing of a promoter have that opportunity and they don't have to pay the sparring partners. For example, if you are signed to Top Rank, you go to Hollywood for a week of sparring at the Wild Card, or to whatever gym in Las Vegas.
If you pay attention to such things you would know what gyms are a current hotspot for your weight class and go there. If you used the Wild Card in this fashion, the gym got a percentage of your purse as a fee.
Also, if you have a connected manager or advisor, a lot of doors open for you. For example, my partner is advising a bantamweight that is 10-0 that you have never heard of, but will shortly. The young man has been sparring regularly with the likes of Rigondeaux, Shakur Stevenson and Oubili (forgot the first name).

 

And Jimmy Ellis.

 

Jack Dempsey.

It's a shame that he didn't give more of his sparring partners a title shot!