I've done this myself with my MIG welder, and it's held up fine.
Shouldn't cost more than $20 to have someone do it, maybe less.  Replace
or weld any broken/missing braces while you are under there.

"Cooper, Jonathan R." wrote:
>
> First subject.
> The three cornered  Collar on our  catalytic converter cracked off the body
> of the converter the other day. It is a nice clean break and it looks like
> the weld simply failed. I suspect that the brace failed first allowing it to
> flex up and down. Is this something that  I can take to a welding shop and
> have them weld. The cat "looks good" on the inside and I don't want to spend
> $100 that I don't have to.
>
--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Daily driver since 1969)
'74 MGB GT (Restoring sloooowly)

Personal mechanic for:
'70 MGB GT (Daughter's)

Assisting on Restoration (and spending OPM):
'72 MGB GT (Was daughter's, now son's)
'64 MGB (Son's)

Stripped and gone but their parts live on:
'68 MGB, '73 MGB, '67 MGB GT