Stem length?

I'm planning to use a regular Cinelli race bar. Turn it around an cut it.
It goes on a Motobecane from early 80s. I believe the size of the rame is 60.
And I'm 183cm with long arms... :-)

What's a "bar spin"?

Based on this I would say that it may be too long a reach and on long journeys you will be over extending your shoulder/trapeze muscles. Resulting in shoulder and neck ache