Can I integrate with Mustang Shaker 500?

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I am new, so this may have been addressed before, but I would appreciate being indulged. I just bought a 2005 Mustang Convertable with the Shaker 500 system. Took a nice Alpine deck, amp, and two Focal speakers out of my 97 'stang. I like the subs and general layout of the 500, but I don't like the deck, plus, I will not be happy leaving a high end Alpine/Focal system on a shelf. I was told by Hawk electronics that you cannot integrate, I have to tear the whole thing out and replace all components, and that they can't even replace the subs in door.

Can at least replace the deck and keep the speakers and amps, or even replace the deck and two front mains and keep the subs and rears, even use my alpine amp to add in??

Thanks