The Teamsters also endorsed Nixon, Ford, Reagan, and GHW Bush for president.
As to Hoffa, I’d never heard that. Since Hoffa had already been convicted when Reagan was running for Governor, that doesn’t sound right.
At the time of the gubernatorial election, there was a big union power struggle going on as Cesar Chavez and his lefties from the NFWA were merged into the AFL-CIO. The Teamsters didn’t like Chavez and his commie buddies, at all.
Hoffa was president of the Teamsters when Reagan was president of the Screen Actors Guild. Before the 1962 Governor's race Hoffa pushed Reagan to run and offered union support. Reagan didn't do it but some people think it was Hoffa who first put the idea in his head.
Roy Williams used to say that Hoffa pestered Reagan about running and Reagan got sick of hearing it. I don't know if that's right or not but that's what Williams used to say.