[Tekkit classic Id conflicts with Thaumcraft2]

Hi, as the topic says im having a id conflict with thaumcraft2, i just wana know what how to change the ids, and how to know what to change them to. like what empty numbers can i use?

 

Error log follows

 

 

42 mods loaded
Optifine OptiFine_1.2.5_HD_S_C6
Minecraft Forge 3.3.8.164
FML v2.2.106.176
Forge Mod Loader version 2.2.106.176 for Minecraft 1.2.5
    mod_MinecraftForge : Initialized (modpack.jar)
    mod_CodeChickenCore : Initialized (modpack.jar)
    mod_NotEnoughItems : Initialized (modpack.jar)
    mod_ReiMinimap : Initialized ([1.2.5]ReiMinimap_v3.2_04.zip)
    mod_IC2AdvancedMachines : Initialized (AdvancedMachines_4.0_client.zip)
    mod_BuildCraftCore : Initialized (buildcraft-client-A-core-2.2.14.zip)
    mod_BuildCraftBuilders : Initialized (buildcraft-client-B-builders-2.2.14.zip)
    mod_BuildCraftEnergy : Initialized (buildcraft-client-B-energy-2.2.14.zip)
    mod_BuildCraftFactory : Initialized (buildcraft-client-B-factory-2.2.14.zip)
    mod_BuildCraftTransport : Initialized (buildcraft-client-B-transport-2.2.14.zip)
    mod_AdditionalPipes : Initialized (buildcraft-client-DA-additionalpipes-2.1.3.zip)
    mod_ccSensors : Initialized (ccSensors-client-MC125-B017pr1.zip)
    mod_CCTurtle : Initialized (ComputerCraft)
    mod_ComputerCraft : Initialized (ComputerCraft)
    mod_EE : Initialized (EE2ClientV1.4.6.5.jar)
    mod_EnderStorage : Initialized (EnderStorage-Client 1.1.3.zip)
    mod_IC2NuclearControl : Initialized (IC2NuclearControl_client_v1.1.10b.zip)
    mod_ImmibisCore : Initialized (immibis-core_49.1.1_for_1.2.5-client.jar)
    mod_IC2 : Pre-initialized (industrialcraft-2-client_1.97.jar)
    mod_InvTweaks : Pre-initialized (InvTweaks-1.41b-1.2.4.zip)
    mod_MAtmos_forModLoader : Pre-initialized (MAtmos_packaged.zip)
    mod_ModularForceFieldSystem : Pre-initialized (mffs_rev7_for_1.2.5-client.zip)
    mod_IC2_ChargingBench : Pre-initialized (mod_chargingbench-client-1.95b-1.2.5-r1.zip)
    mod_CompactSolars : Pre-initialized (mod_compactsolars-client-2.3.2.10.zip)
    mod_IronChest : Pre-initialized (mod_ironchests-client-3.8.0.40.zip)
    mod_NetherOres : Pre-initialized (NetherOres_Client_1.2.1.zip)
    mod_PowerConverters : Pre-initialized (PowerConverters_Client_1.3.4.zip)
    mod_Railcraft : Pre-initialized (Railcraft_Client_5.3.3.zip)
    mod_RedPowerControl : Pre-initialized (RedPowerControl-2.0pr5b2.zip)
    mod_RedPowerCore : Pre-initialized (RedPowerCore-2.0pr5b2.zip)
    mod_RedPowerLighting : Pre-initialized (RedPowerLighting-2.0pr5b2.zip)
    mod_RedPowerLogic : Pre-initialized (RedPowerLogic-2.0pr5b2.zip)
    mod_RedPowerMachine : Pre-initialized (RedPowerMachine-2.0pr5b2.zip)
    mod_RedPowerWiring : Pre-initialized (RedPowerWiring-2.0pr5b2.zip)
    mod_RedPowerWorld : Pre-initialized (RedPowerWorld-2.0pr5b2.zip)
    mod_ThaumCraft : Pre-initialized (ThaumCraft2.1.6d.zip)
    mod_TubeStuff : Pre-initialized (tubestuff_49.1.2_for_1.2.5-client.jar)
    Balkon's WeaponMod : Pre-initialized (WeaponMod.zip)
    mod_WirelessRedstoneAddons : Pre-initialized (WR-CBE Addons-Client 1.2.2.3.zip)
    mod_WirelessRedstoneCore : Pre-initialized (WR-CBE Core-Client 1.2.2.3.zip)
    mod_WirelessRedstoneRedPower : Pre-initialized (WR-CBE RedPower-Client 1.2.2.1.zip)
    mod_ImmiChunkLoaders : Pre-initialized (zdimensional-anchor_rev3.2_for_1.2.5-client.jar)


      Minecraft has crashed!      
      ----------------------      

Minecraft has stopped running because it encountered a problem.




--- BEGIN ERROR REPORT b8263065 --------
Generated 8/4/14 9:05 AM

Minecraft: Minecraft 1.2.5
OS: Windows 7 (amd64) version 6.1
Java: 1.7.0_15, Oracle Corporation
VM: Java HotSpot 64-Bit Server VM (mixed mode), Oracle Corporation
LWJGL: 2.9.0
OpenGL: GeForce GTX 770/PCIe/SSE2 version 4.4.0, NVIDIA Corporation

java.lang.IllegalArgumentException: Slot 248 is already occupied by thaumcraft.world.BlockCustomLeaves@52099a1b when adding ic2.common.BlockTex@74648cb0
    at pb.<init>(Block.java:251)
    at pb.<init>(Block.java:284)
    at ic2.platform.BlockCommon.<init>(BlockCommon.java:12)
    at ic2.common.BlockTex.<init>(BlockTex.java:30)
    at mod_IC2.load(mod_IC2.java:211)
    at cpw.mods.fml.common.modloader.ModLoaderModContainer.init(ModLoaderModContainer.java:356)
    at cpw.mods.fml.common.Loader.modInit(Loader.java:273)
    at cpw.mods.fml.common.Loader.initializeMods(Loader.java:628)
    at cpw.mods.fml.client.FMLClientHandler.onLoadComplete(FMLClientHandler.java:223)
    at net.minecraft.client.Minecraft.a(Minecraft.java:429)
    at net.minecraft.client.Minecraft.run(Minecraft.java:738)
    at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT 9e413e58 ----------