People from Project 2025 are writing official government memorandums.
But that's the problem here: no amount of evidence short of an admission from Trump is going to "prove" it to you, and Trump will deny this, all while Project 2025 is enacted by the people who wrote it with the unspoken blessing of the GOP.
A spade is spade.
You can confirm on the GOP website that the GOP platform is called agenda 47. You can also read agenda 47. This was published prior to the election.
Agenda 47 and project 2025 have very different approaches to matters like abortion. So far the evidence has been that the GOP supports the GOP‘s own platform in this regard, for example there’s no federal ban on abortion pills, which is part of project 2025 but not part of the GOP’s platform agenda 47.
If you are alleging a conspiracy that agenda 47 was the smoke screen in favour of the heritage foundation’s project 2025 then you will need to provide some kind of evidence for this conspiracy.