petrol tank

[misty]

Hi all
the tank came of a mk4 or 1500 spitfire and that is where the problem is ,on this tank the outlet is at the top whereas the on the mk1,2,3, it was on the bottom, so what i did was ,i removed the pipe from the top and sealed it with a threaded cap in mild steel , great that sorted that, the other little pip at the top i left to be the breather ,great that sorted that, NOW here comes the next problem ,in order for the bike filter and pump to work properly, i need to drill a hole in the bottom of the tank and weld on a 10mm plumbing socket and then add the 8mm pipe with a nipple screwed in to the socket, great that is that problem solved BUT WELDING A PETROL TANK??????? NOT SO EASY has anyone any ideas ??