Do you mean the notes in the notes tab or the data in the tracking tab?

Apologies for any confusion. All data from the "tracking" tab. 

After a lead is converted to an opportunity they wish to be able to go to the "tracking" tab in the opportunity and see all the data from when it was lead.

Hope that makes a bit more sense?

The tracking data is read from the progress table associated with the entity. These are controlled by the DLL. I would suggest that it can't be done because the tracking is linked to the workflow progress on the lead. You can't put the lead tracking on the opportunity as the records would show that the tracking started before the opportunity was created.

There is a button called View Lead on the Summary page for an Opportunity converted from a Lead.  Have you considered changing the behaviour to call the Lead Tracking tab for the original lead?  You would need to use the Client Side API.