There's no easy method or tool to achieve what you're after. Primarily because of the following differences:
MCP:
[ModCoderPack] was created to help mod creators to decompile, change and recompile the Minecraft classes.
Forge:
[Forge] is a massive API and mod loader used by modders to hook into Minecraft code and create mods. Forge contains numerous hooks into the Minecraft game engine, allowing modders to create mods with a high level of compatibility
So Forge creates an accessible API for developing easily maintainable mods whereas MCP is used to create modified versions of Minecraft client/server, distinct from the concept of a mod.
Forge is built on top of MCP and adds lots of new functionality. Depending on your mods complexity, it would take a tremendous amount of effort to rewrite the mod directly into Minecraft's deobfuscated source code.
Unless you have very good reasons to need this, like the creator of MCP said, just use Forge!
