TBM:
These are FAA based answers.
If you are asking to physically change aircraft from an N to a 212 with a new data plate: no conversion possible.
Define civilian use. If you are asking to operate the N for civilian commercial operations, then it is possible. But the best you can probably get is a Restricted airworthiness certificate.
But even under a Restricted category I would think it is economically unfeasible to replace or verify times/origins on all required components.
Check out FAA Order 8130.2G
http://www.faa.gov/regulations_polic...mentid/1027070
Good luck!
W1