Imprinting Variable Data..

We have a client that is wanting 20,000 full color mailers printed. The complication is that they want each one to have a unique bar code on one side linked to the mailing address listed on the other side. It is 11x17 and full color with heavy coverage on both sides including full bleeds.

Normally we would just run this on the press but and then imprint the necessary information on a laser printer but with so many I am wondering how others might handle this.