Mac Pro Mid 2012 Video card, SSD, and Mojave upgrade

[linkmaster6]

Good day everyone,

I've gotten my hands on a mid-2012 Mac Pro (Quad core 3.2GHz) that is in need of being upgraded to Mojave and needed a few other upgrades as well.
It still contained the original Nvidia GT 120, which from my research online wouldn't make the cut to upgrade to Mojave. So after taking a quick peak at Apple's list of verified working cards (Mac pro and Mojave) I'd settled on upgrading to the MSI Radeon RX 560 (MSI-RX560AEROITX4GOC-R).
Also during my pre-update assessment I noted from the awfully rough sounding hard drive it was time to replace that as well and got a Samsung EVO 1 TB SSD preloaded with Mojave and a SATA bay adapter to bring it all together.

So with all the items now in hand I have begun the process of upgrading. First I installed the new video card, booted with the original HD, and checked that video card showed as Metal supported.
Next I shut it down and installed the SSD and removed the original HD, booted it up and just get greeted with a screen full of white noise, left it to run for awhile but it doesn't get any further than this. Hard power off, restarted, ran a PRAM reset, same.
So swapped the original back in, boots fine. Connected the SSD (adapter and all) to a USB connector, its browsable, appears to contain everything it needs to boot.

So what might I be missing in this grand equation?

 

[JohnCL]

Do you have bootable install media for Mojave? It may need a firmware update that will happen when it boots from media. My MacPro did this on the initial install, so I would try booting to install media vs. a hard drive that already has Mojave installed.

 

[linkmaster6]

I don't at the moment. But I did get to boot to usable screen and ran through the first time setup screens with Mojave and imported the user account data from the old hard drive. It was fortunate my daughter had woken from a dream and it had more time to run and came up on its own.

I believe I will still need to get a firmware update perform, if I can get passed that screen again how easy is it to start the update?

 

[linkmaster6]

So made a bit of progress, got the firmware update pushed through by starting the Mojave update on the old hard drive. So now I have video from the boot screen clear to the OS. But I still have 2 issues....

If I allow this to go to sleep and wake it up, I get the staticy white noise screen or if I tell it to restart I get the same.

Also even though I've signed this account out I can't seem to get rid of it. I've sign in with my own, but every time I try to install updates it keeps asking me to log into this other account.