Cross Domain Tracking (without GA) on a second domain I don't own

Hello all,

I was wondering if anyone can give me advice on cross domain tracking:

I am planning on running a campaign where I drive leads on one domain, retarget the lead on AdRoll and Email and drive them to a second domain where they can convert.

What are my options with regards to building audiences and conversion tracking across domains. I need to measure who converts of the traffic I drive to domain 2 out of the leads I have converted from domain 1.

My main issue is that the second domain is a client website, so I have to make it as easy as possible to implement any tracking scripts, the first domain is my own so I can add whatever is required.

I know through AdRoll I can set up conversion tracking and smart pixels on both websites – but ideally I want more in depth conversion data and the ability to know which traffic I send to them converts, as well as name, basket value and so on from both domain 1 and domain 2.

In an idea scenario I would have a tag manager that I can place on the clients domain, and where I can place conversion tracking from a 3rd party analytics/tracking provider as well as any pixels from retargeting platforms (getting cross domain tracking set up on Google would be too much of a hassle with the client). Is this possible to do? If not does anyone have any clever ways they use cross-domain tracking?

I hope that makes sense, and sorry if it’s a basic question. I’ve been trying to work it out for the past few days but haven’t been able to.

Thanks

Pedro