Could make a mod using parts from another?

I am working on a Volvo 240 wagon and I found out that making a a car from scratch is not very easy. Could I use an existing Volvo 240 sedan I found, (https://www.beamng.com/threads/volvo-242-le.35188/ or https://www.worldofmods.com/beamng/cars/1659-volvo-242-turbo-evolution.html ) and make it into a wagon and then upload it? That would make it easier because they have a similar frame and interior.

 

You could probably make it into a wagon but you may have to ask permission in order to upload it.

 

Who would I ask?

 

The author of the mod.

 

You will still need to modify the jbeam too