Please fully read this first post, you will probably find that you have one or more problems described into the various notes below. Mojave will only install if you have upgraded your BootROM to the current release and your Mac Pro have a Metal capable GPU*. If you are trying to install Mojave...
No, it’s not the latest. The latest (final) version is 144.0.0.0.0.0
Go to the post above, and click on the link provided by dvbcheck to read what is needed to upgrade.
You can also contact @tsialex for a newly reconstructed and improved bootrom.