The most flexible way is probably to do this with a Salt recipe (since Salt has already become quite central in Qubes). You will need to write a set of Salt files for
qubesctl to do the job from each or your Qubes machines’ dom0.
And you will need to install them into every machine’s dom0.
To go beyond would require knowing more about what you’re doing. You way want to do the tedious work of getting those files there manually. But if you expect that these customizations will evolve with time (and even if we don’t think about that initially, they usually do ), you’d be better off with replacing this manual task with (manually) installing an automated way of propagating future versions of those files. To leverage existing mechanisms (including authentication of what enters your dom0), this will involve packaging them in a RPM and referencing your custom yum repo in their dom0.
Now to replace that manual work on every such machine, you may want to build your own custom installation image to include that RPM.