In the William storyline, they mention that the place "Started as a partnership, but one of the partners killed himself" And since then its been hemorrhaging money. In the MiB line, he mentions its been 35 years since Arnold's death. The park would have trouble staying open running in the red for 35 years. Plus, the William's Brother-in-law talks about Arnold's death, it was like it'd happened more recently than 35 years ago. In that same encounter, the MiB makes mention that he helped save the park when Arnold almost took it down, but its carefully worded not to say he had any direct involvement with Arnold's death (though its implied on first listen) This combined with with the 1st episode dropping that its been 30 years since the last incident in the park as of the MiB timeline, lines the timelines up nicely.
The only thing that's not lining up at all is how several Delores flashbacks have the MiB in the same timeline as she shares with William.
