Minecraft mods like this are supposed to make Minecraft more realistic

OK, a normal Block is automatic generated as Item, when you use custom Render(Model)
you need to implement a few things.
look on the forum from forge and search for render block as Item!
there i found what i need longer time ago, the code is near the same from 1.2.5 until now.
when you found a old tutorial will work, too a few little changes
the main change is in the Block Render file.
you need to add a few parts:
to the public class declaration add this:
extends TileEntitySpecialRenderer implements ISimpleBlockRenderingHandler

code:
@Override
public boolean renderWorldBlock(IBlockAccess world, int x, int y, int z,Block block, int modelId, RenderBlocks renderer) {
// TODO Auto-generated method stub
return false;
}

@Override
public boolean shouldRender3DInInventory() {
// TODO Auto-generated method stub
return true;
}
@Override
public int getRenderId() {
// TODO Auto-generated method stub
return BetterWorldCoreBlocks.renderAluBlockID;
}
replace the RenderAluBlockID with your render ID
Hope it help you

Sorry only Forge