Facebook attribution when sending data from a webhook

So I need to setup tracking on click funnels, the only way I can get data from click funnels is by a webhook.

The issue is I can’t control what data they put in the webhook so I don’t know if they will add _fbc in it at all…

But, I have a page view event setup with GTM web and server container. I use data tag to send events to the server.

If I add _fbc inside the page view event of the data tag which will carry it over to the server, will the purchase tag on the server be able to pick up that _fbc and attribute the sale correctly inside facebook?

No, that’s not gonna work. For attribution to work correctly - you need all payload data to be in the webhook, including fbc, fbp, user ip address and user agent.
And of course other conversion data like value, currency.

If you have user data in your webhook - attribution can partially work on that data, but it will be far from good performance.