Hi Dave,
The radiator shops were probably trying to scare you off. Even if you would have said yes to the 900 bucks, they still would have found another reason not to have done it.
Back in the late 70's and 80's there were quite a few good old school radiator shops around Dallas. Now there are none.
The ones that supposedly "repair" radiators automatically tell you your's needs a recore, then try to sell you a new one at twice what you pay on the internet!
I do all my repairs myself these days. It looks like crap, but gets the job done!
Thanks, David