Trying to convert an ARF Mustang to an RAF mustang..
looking to remove the decals from a foam ARF without destroying it
any suggestions on decal removal from a foam ARF?

It could depend on the ARF itself. A cheap, low density unit might just fall apart when taking off the decals where a more expensive, high density might handle the removal better. It would add some weight but you could also try just a primer coat and then add your new decals.

BTW, during WWII the New Zealanders figured out an easy way to convert a USN F4 Corsair to a NZRAF Corsair - they just painted a roundel over the star. That was it.