I'm pritty sure, you gotta heat the sump up super hot before you start the welding. Just get a workshop to weld it. You want it done right, can u imagine doing it yourself and its not done right, pulling the motor out, fitting it, and than putting the motor back in only to find it leaks, or cracks on your first launch. The sump has a fark load of force going though it, if its not done right, you will break weaken it. Also make sure it's bolted down to somthing flat and left there to cold right down, so it don't twist or do anything crazy.