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My brother-in-law is restoring a 1929 Tudor. He does the physical work and I agreed to help him on researching. I have some question regarding holes in the lower firewall. I know some are supposed to be there and others have probably been added by previous owners.

Which ones will he need to patched up?

1. I assume holes in circles in 1, 3 & 4 should be patched.
Does anyone know why the holes would have been added inside circle #1?
I assume the holes in circle # 3 & 4 were for a heater core, but not original.

2. The holes in circle # 2, 5 & 6 appear to be original, if so what were the used for?

Thank you for your knowledge!