Congratulations on planning ahead for this job. I hope you have a boat yard that specializes in wood boats. There are still enough old shrimpers around here to support a great wood boat yard. I'm convinced that frequent, short hauls are the best wood boat care. Wishing you many worst plank hauls.
Being the skeptic (cynic) that I am, I would expect poor installation of the older transducers and assess the installations to eliminate the worst ones.
I like the idea of repurposing good ones and keeping new ones for spares.
If the GB is double planked you might need a double plug to allow for movement between planks.