Rather than bend the tempo of Cubase to the analog track, a system I use is to set Cubase tempo so it tracks as closely as I can get it ie.120.045bpm.
I do this by setting a beat at the beginning and adjusting computer bpm by looking at barlines further and further down the track. Since reel to reel tape machines wow and flutter to some extent, I then cut the analog track every few bars or beats as necessary to get it to sit nicely alongside a new click track.
Whilst this isn’t purist, the result is in perfect time (relative to computer clock - I won’t debate musical merit here). I finally crossfade any overlaps and fill any tiny gaps by pulling one side of the cut towards the other. Once you overlay say a new bass drum, or drum loop, the result is very close to perfect.
You may need to process loops or set them to play at the exact tempo. I rarely use pre-made patterns, so the tempo not being an exact number of BPM isn’t a problem for me.