Go to a JY, cut off another one of those plugs but with way more wire to work with. Solder it back on and then do it the right way.
I have not run into an application where there is not an adapter harness made for it for like... well ever. You should never have to cut a harness to install a radio. Even bypassing the stock amp there are adapters.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.