welding a ZXR alloy tank?

G'day again..
Anyone happen to know what type of aluminium is used on the ZXR750 fuel tanks? I'm thinking probably 6061-T6?
Reason is, I need to do a welded modification to a spare alloy fuel tank I have to make it suitable for road use. Obviously in a previous life it has been used on a race bike & the underside has been deepened to increase capacity, but it won't fit on a standard bike with the standard coils & airbox in place.
Advice on what aluminium to use from anyone with experience welding these tanks would be much appreciated.
Jason
Anyone happen to know what type of aluminium is used on the ZXR750 fuel tanks? I'm thinking probably 6061-T6?
Reason is, I need to do a welded modification to a spare alloy fuel tank I have to make it suitable for road use. Obviously in a previous life it has been used on a race bike & the underside has been deepened to increase capacity, but it won't fit on a standard bike with the standard coils & airbox in place.
Advice on what aluminium to use from anyone with experience welding these tanks would be much appreciated.
Jason