Create a new sync account.

I want the data contained in the old sync, not a fresh start

Sorry, there's no way around the verification getting sent to the email address of record for that Sync account.

Sync was not intended to be a "cloud" for data storage, it was made to synchronize Firefox data across multiple devices whenever Firefox is running on each of those devices. Your data would still be on another device, if you had one already connected to Sync.

And when you "add" a device to the Sync account the Sync system usually sends an email for verification purposes, especially when there is a time lag between when each "new" device is connected to the Sync service. IOW, when setting up a new Sync account and connecting multiple devices within a certain time frame, an email probably wouldn't be sent when the 2nd device is connected.

I foresaw a problem such as this when the original Weave extension was being transitioned into the built-in Sync for Firefox 4.0 back in Dec 2010. and the "username" field was eliminated in deference to using the user's email address instead. But my "warning" to Mozilla was explained away due to design parameters of the Sync service.