The stock spring bar as purchased from R.R is 7075 T6 aluminum and it's been my understanding that 7075 T6 aluminun is not a weldable grade of aluminum. If you want to study the properties of this grade of aluminum , you'll find what you need to know in Machineriys Handbook What it is is spring aluminum and the phisical properties are altered with high heat applications. I'd be real careful here
