Try this site:
http://www.damonrinard.com/spocalc.htm
They have a spoke length calculator (needs excel to read) which has the Ambrosio Elite.
I would strongly, strongly, strongly recommend using new spokes (in which case the length is not really an issue). Spokes are elastic and become un-elastic over time. Eventually they fatigue to the point they fail. New spokes will make things much easier when building up a new wheel. Consistent, predictable tension. Also shiny spokes look nice.
Nevertheless, if you want to use the old spokes, I'll save you some time and c/p the results (+/- 1 mm):
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hope this helps
cdr