You're right, T3 is completely different from T4. If you want to build JA Property in T4, it's the same like creating a new template for T4. It will really take time.
My suggestion is:
1/ You can look for another T4 based template in the page above
2/ If you like the design of JA Property template and want to build in T4 framework, you can consider to hire a developer to implement it for you. I can introduce for you but it would take time and effort.