I just did this upgrade a few months ago on my sons 2020 FFE with a JL3 TCU and the Ford PIFA antenna. Happy to provide any assistance I can if you still need. I used this site and printed instruction on how to remove the rear deck and panels.
https://www.fofusion2.com/ford_fusion_2013v_2020_service_manual-1942.html
https://www.fofusion2.com/ford_fusion_interior_trim_and_ornamentation-2705.html
You’ll likely need to source your own bolt for the PIFA antenna - I got my antenna from a junkyard so it was just the antenna. The connector cable I used was this one:
https://www.amazon.com/gp/product/B07P5CTDFY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1