I am a senior developer worked in inverstment bank for 10 year. I have lots of experience in enterpise application which using maven, ant to do automation build and testing. I have done many migration like your requirement.
To complete your project, I will
1. List all your current dependency and their versions.
2. Add all jars into single project to test if they have conflict
3. Put your modules in one by one and fix all conflict.
4. Implement the ant build, test and deploy logic
Cheers, hope I can help you.