Mec,
a Mig welder will be cheaper to buy and run than a Tig machine, plus the Mig should be fine for any work you may need to carry out on a 2CV, or a 3CV for that matter...
Some hints on using a mig welder can be found on this forum, all in English I'm afraid, but I'd take a bet that there may already be someone from Argentina who's a member of the site...
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http://www.mig-welding.co.uk/mig.htm >
ken