Looks like you bought a bare Z800 motherboard and are working on a project.....
Some of the earlier workstations like the xw6400 had an option under the last tab in BIOS to disable recoverable F1 error alerts. All the ones you show I believe are recoverable, and that would be proven if you can F1 and the motherboard will proceed into full boot. However, you might be stuck with having to do that each time you boot the Z800.
I just checked on my Z600 project box, which has the 4/16 new BIOS (which you should be using, Z800 version). That F1 hide option is not there on mine, and I bet it will not be there for the Z800 either.
The HP fans for these workstations generally are PWM with motherboard firmware programming to throttle down their speeds so that if needed the motherboard can ramp them up in speed to account for higher thermal states. Most you don't even need to get the exact HP fan..... for example, you can get a HP fan from another older HP workstation, plug it in, and it will be happy. I'd try to get HP fans with the correct header plugs, used off eBay. I have part numbers for some of these or ones that could be substituted in. I'd suggest using HP heatsink/fan(s) for your project due to the critical nature of those.
Your processor(s) must draw over 95W to trigger the request for the higher capacity heatsink/fan combo..... you can read up on that here under "Performance Heatsink/fan" and ones of that type for the Z600 and Z400 may fit just fine in your Z800.... same sockets.
There are different fan headers on the motherboard, and I can look at mine to let you know the types for each of those. Some are standard white PWM, some are 5 pin, and the rear chassis 2 fans got combined into one 6 pin header for my Z600 and maybe your Z800.
Enjoy your project.... maybe post some pics here for fun.