I'm going to modify my moutain bike and need to know how to weld it back together with pivot points for a rear shock. The bike is made out of 7005 aluminium I think. The welds must be extreamly strong as they will be subject to about 900 lbs of stress. I have never welded anything before but I have seen it done. I don't know what type of welding, MIG or TIG, to use and what type of filler, if any, I should use. I would also like to know about any prep work needed to be done to the metal and anything that might affect the stregnth of the weld such as air contaminates, ambient temperature, etc.