[prktkljokr]

I had a extension housing for a C4 gearbox modified once with mount for a transfer case, the guy who did it welded aluminium boats ( a friend of a friend), it out lasted the vehicle it was put in .

I doubt if it would be much different alloy than any other automotive aluminium casting, I would try someone who does aluminium welding even cylinder heads and see if they can weld it up.

As long as you do not have any other fractures around the hole leading to anything machined you should be fine, you will have to completely strip the casing and have it hot washed etc to get the alloy clean for welding.