I have been trying to implement this for awhile but with little success.  I have added methods that work just fine for blocks with the normal block IDs of 255 and below but it has trouble rendering for anything over.

 

You can add this where you would like but I used ModLoader class for simplicity.

private static ArrayList<Integer> EndermenCarry = new ArrayList();
    public static void addToEndermenCarry(int blockID)
    {
        EndermenCarry.add(blockID);
    }
    
    public static ArrayList<Integer> getEndermenCarry()
    {
        return EndermenCarry;
    }

 

This goes in the static{} of EntityEnderman class after the other code.

for (int i = 0; i < ModLoader.getEndermenCarry().size(); i++) {
            canCarryBlocks[ModLoader.getEndermenCarry().get(i)] = true;
        }

 

I have gotten this to work with anything with a normal BlockID.

 

Error it presents when it crashes if it crashes:

 

java.lang.ArrayIndexOutOfBoundsException: -72

at net.minecraft.src.ExtendedBlockStorage.setExtBlockID(ExtendedBlockStorage.java:79)

at net.minecraft.src.Chunk.setBlockIDWithMetadata(Chunk.java:629)

at net.minecraft.src.World.setBlockAndMetadata(World.java:669)

at net.minecraft.src.World.setBlockAndMetadataWithNotify(World.java:821)

at net.minecraft.src.EntityEnderman.onLivingUpdate(EntityEnderman.java:169)

at net.minecraft.src.EntityLiving.onUpdate(EntityLiving.java:662)

at net.minecraft.src.EntityMob.onUpdate(EntityMob.java:35)

at net.minecraft.src.World.updateEntityWithOptionalForce(World.java:2194)

at net.minecraft.src.World.updateEntity(World.java:2165)

at net.minecraft.src.World.updateEntities(World.java:2047)

at net.minecraft.client.Minecraft.runTick(Minecraft.java:1867)

at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:822)

at net.minecraft.client.Minecraft.run(Minecraft.java:750)

at java.lang.Thread.run(Thread.java:722)

 

 

I have attempted to tweak the code to work but it doesn't come up with any easy solutions.

ModLoader.getPrivateValue(EntityEnderman.class, 0)[myBlock.blockID] = true

Mind if I ask what build you are using?  I can't seem to find a getPrivateValue that only accepts 2 variables.