I hate reusing old stuff - why not just install all new mains? If they fail - they'll blame the EC - if you break it during disassembly, you would be blamed and on the hook to replace it - if it doesn't work after you reinstall it - even though you didn't do anything wrong you'll get blamed - you'll get blamed for anything for the next year - don't use old crap. Plus, you drive down the price on the job, and when a company who believes in doing things right bids the job - they lose it to companies that are piecing the job together.
I know I'm not in this business to help out the guy who needs a lot of work done cheaply. I do lose bids to guys who cut corners and the people who are comparing the bids aren't looking at the same job - apples and oranges - but all they see is the price and think they are getting the same job for a lot less money. Why do most of the job right? Heck, why not just buy some sheet metal and repair the rusted out cabinet - that would save the owner a ton of money - and you'll be out of there in no time.
BTW - I have a saying - If money is a problem, come back when it's not!