Engine swapping in career mode

Hello! I just bought a Cherrier Picnic Cargo in Career Mode and an ETK K1. I want to swap engines - put the 2.5 ETK K1 engine in the Cherrier Picnic. Yet, when I go to my computer, I can't seem to be able to mount the 2.5 in the Picnic. The only options are the original engine and a weaker 1.1 engine. Also can't seem to find the ''Buy Parts'' button. Devs should work more on the game, it's really annoying. Anyway, does someone have an answer to this? Thank you!

 

you can't

 

make an engine swap mod for it
https://www.beamng.com/threads/tutorial-how-to-do-engine-swaps-with-pictures.56000/\

 

oof. beamng devs are annoying