I dont know if everybody know how to do this but I found a way to recover the previous version engines.
Go to Documents and open the Automation folder. Then open the Engines folder. Open the engines using Notepad.
When opened, press CTRL+F and write “GameVersion” (without quotation marks). After this you will see the line where is the engine version (the previous one was 1198). Change it to 1317.
Done 
(worked on all my 130 engines)
Yes, but the reason that version field is there is to stop old version engines from behaving strangely or crashing in the current version, so if you get any strange issues that’ll be why 
Alright ^^
Can I do the same with platforms? Or is there no chance becacuse of aerodynamic stuff. I wouldn’t mind adding suspensions and brakes, etc to them, I just don’t want to remake them all again.
No one keeps you from trying
is an import script very hard to do?
like recalculate everything from old to new?
Probably not too hard to do, no, have a go if you like, but we will not spend time on it as you might understand.
I dont know if this works on platforms. I tried only on engines.
Sorry dev team but I love my engines. I hope you can understand this 
as i only have skills in car repairs/mods, photography and some music, i have no idea on how coding stuff works
Doesn’t work on platforms, there’s stuff missing in the LUA file that the new version needs (fails on with Nil on Family)
I going to have a go at “transplanting values” from the original to a new version of the LUA just out of curiosity to see what happens.
**EDIT - Had a look at the LUA files, for an older platform and a “blank” of the same bodyshell, lots of things in different places, new tables inserted inbetween others, etc. I think it would be easier to recreate them from scratch in the game (as it should be probably)