1974 Peavey 412 speaker replacement suitable for bass?

[sutarappa]

Hello.

I am researching bass speaker options to replace the blown stock Eminence drivers in this large, vented 4x12. Preferably resulting in a 4ohm cab. Anyone have suggestions or experience?

I would love to find 16 ohm voice coil replacements that might work; I hate to throw out good magnets, steel, cones, etc.

Pics attached, thanks.