NOTE: This assumes you have the Google Shopping App already installed for you Google Ads conversion tracking, but I *think* it should still work even if you don't.
A full writeup of this and other tweaks to make to Shopify's conversion tracking available here:
Fantastic! I was having a difficult time figuring out how to pull this off with the Google channel already activated.
EDIT: Google support was able to verify that I have it correctly set up using the settings I just pasted. So maybe there are multiple ways of doing it?