If that is where I think it is, it will, as Isuzurover says, require competent, professional standard welding, with all mechanical parts removed from the housing. Since you need to do this, you may want to think about replacing the housing or perhaps the entire rear axle!
Unfortunately, poorly thought out "reinforcements" are a perennial problem, albeit usually on chassis rather than axle housings. (and not just aftermarket modifications - manufacturers are not blameless)
John
John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
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