H.264 – MP4 has standard frame sizes.
You may be able to force that frame size using different software but don't expect it to be 100% successful all the time.
If you have some kind of a playback system that is demanding that frame size I need to check into their specifications of him and coding technique because it is not standard. It would help if we knew why you need that exact frame size.
The client uses several projectors that project onto that screen size. That is what they told us we need.
Sorry about the second paragraph I posted above. -- Voice to text on my phone.
As I stated and Roei reenforced you'll need a special container. AE and the Media Encoder won't allow you to do this so you'll have to render to a mezzanine codec (production format digital intermediate) that will accept this format and then use 3rd party solutions to render using another format like h.264. Contact your client and ask them what they use to encode and then use that.
as Rick mentioned - this is not a standard file size. in my experience, the projectors have a limit for projecting the video say HD Projectors are common, 4K maybe no so much - and you actually need more than that. The setup is carefully placed HD projectors in an overlapping setup so that you can project as many pixels as you want by producing as much video files as needed for each segment. so 10xHD video in overlapping can produce +10k projection for example
as for the encoding, just to be clear, you can encode H.265 in AME and it works fine. I have not used that codec personally but exporting in the dimensions OP specified passes through and the file plays using VLC Player.
so ask your client exactly how is this going to play and what exactly do you need to give him. if it's one mp4 file in the resolution you specified - you can.