To quote the MIT License:
Copyright [YEAR] [COPYRIGHT HOLDER]
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
So - you can redistribute modified versions of specific classes from an MIT-licensed project. You'll have to keep the original copyright and license for them, though.
An acceptable approach could be to have such a paragraph in your license (or readme) file:
Classes under the XYZ package were taken from project ABC, Copyright 1999 Original Author.
These classes are licensed under the MIT license. See XYZ-LICENSE.md for additional details.