Here's the easy way:
- Open the 120BPM project.
- Enable snap, and set your Now time at Measure 121 (Tempo +1 because measures start at 1, not 0)
- Hit Shift+M to bring up Set Measure/Beat At Now, enter Measure 86, Beat 1, and OK.
- SONAR will set the initial tempo to 85
around the existing material without altering its playback timing.
- The M:B:T Grid will now be aligned with the MIDI (as well as the audio) at the original tempo of 85 BPM.
- Drag the MIDI out to your desktop and import it (or copy-paste directly into your original project), and you should be good to go.