Since that is a steel frame...I don't know what you have in it or envision it's purpose being you mention it being a cheaper Italian brand...but if I were going to use that bike I would likely look at having a frame shop replace the top tube and powder coat it. I would want to take a long hard look at that frame inside and out to consider it's structural integrity. Also, consider that the heat from your weld likely changed the temper on that tube at a critical spot.