the creator probably is not planning on making a fix for it and making this thing work properly. if the creator wanted, he would have done it way sooner (the last update was from 2017). so the only hope is on modders or someone that has the ability to fix it and make it work properly again (also, sorry for bump, if anyone thinks it is one)
Hey guys, I was looking into it and found a fix someone made in this thread https://www.beamng.com/threads/fiat-one-mod-has-no-part-tree.80867/