How do I do the research

If this is in the wrong forum, a mod can move it for me.

I have a car I want to research the history of, hoping to include the owners names and how long they owned it.

I know the history from now back to about 1998. I have a gap there. If the machine shop that did the engine in 1993 I could probably fill that in.

I know in 1984 who had the car registered.

How do I fill in the gaps???????

Thank You.