[1.7.10] How to add functionality to fire blocks?

[Fynal]

Forge version 1.7.10 - 10.13.2.1230

 

I'm trying to make it so that when a wood log block burns up (is destroyed by a fire block) in the world, it has a chance to turn into a charred log block instead of just disappearing. Then you can mine the charred log for charcoal. However, I (obviously) can't edit the base fire class, and I can't find a forge hook for "block destroyed by fire".

 

How can I make this work? Do I need a coremod?

 

As far as I understand, neither reflection nor access transformers will allow me to add new code to the BlockFire class.

 

Thanks in advance!

[Fynal]

I'm trying to use GameRegistry.addSubstitutionAlias:

 

GameRegistry.addSubstitutionAlias("minecraft:fire", GameRegistry.Type.BLOCK, (new moddedfire()).setHardness(0.0F).setLightLevel(0.0F).setBlockName("fire").setBlockTextureName("fire"));

 

I intentionally set the light level to 0, so that it would be obvious if it worked. I can't seem to get it to work though. It doesn't crash, but any world I load (even a brand new one) tells me I'm using a backup level.dat when I try to open it, and asks if I want to continue. When I hit yes, the world loads normally, but the fire still gives off light.