Classic OEM headunit into new amplifier

[Bjfox1970]

I have a ‘72 Delta 88 convertible.

i am wanting to keep the OEM AM/FM stereo head unit, but run the high level outputs into a modern Bluetooth amp.  The original head unit has common ground outputs and requires 10 ohm speakers.  

I plan on installing modern 4 ohm speakers and powering them with the modern amp. Obviously this system uses floating grounds for the speakers. The amp also requires floating ground high level inputs from a head unit if one is used.  I found a floating ground adapter, however it is designed to use a floating ground head unit with common ground speaker wiring. 

Two questions:

Would it penpossile to just split the common ground output to both input channels on the amp?

And if not:

Is it possible to use the available floating to common ground adapter in reverse?

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