How challenging is it to swap uppers on billet ARs?

I have a billet 308 AR that I'm looking to build a 260 Rem upper for. Manufacturer doesn't sell stripped uppers for their 308 ARs or even complete uppers.

Billet uppers have a tendency to be a little more artistic than forged versions, but I'm assuming the profile should be reasonably consistent where the upper and lower come together from manufacture to manufacture.

Am I being too optimistic?