'64 Barracuda floor pan questions

I'm in the process of partial replacement of the floor pans. I'm welding up the extra holes that the previous owner put in the floorboards. Lots of drilled holes that don't seem to have a purpose.
There are also two small punched slotted holes located under the passenger side bucket seat. (Photos attached) What is the purpose of these holes? Being punched seems to indicate that they were original from the factory. But what are they used for?
There is a series of small holes in the vertical portion of the floor pan behind the rear seat. (Photos attached) Same question, what are they used for? Can they/should they be welded up?
Also attached is a photo of the 4 speed hump that is in the car. Did a '64 originally have a 4 speed hump or did the previous owner add this? The welds on it are not very neat and I suspect that it might have been added.

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