I'm not an expert on such things, but I'd suggest that it's not possible to weld the broken piece back onto the output shaft flange, properly, with the shaft still mounted to the transaxle. Taking this one step further, if you're going to the effort of removing the output shaft from the transaxle, why not just replace it with a good used one? Then you never have to worry about it. This is also a good time to take a good hard look at the transaxle in general. Does it shift smoothly into each gear, are there any leaks, is your ring gear safety wired, etc.? If it has any of these issues, don't put off taking care of them now because it could cost significantly more to fix them later.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.