Good luck. I faced a similar situation a couple years ago. I thought about having my bulkhead rebuilt and then dipping it, but chose to get a td5 bulkhead instead and have it dipped and switched to a newer dash. If you have time, and skill/$ it would be far easier to have yours rebuilt. If you need a dipped bulkhead that is ready to go Ashtree in the UK advertises galvy bulkheads.
1970 SIIA 88, Sold
1996 Disco I, RIP