what is the largest capacity hard drive that can be installed in Mac Pro 2008 MA970LL/A

Greetings What is the largest capacity hard drive that can be installed in Mac Pro 2008 MA970LL/A

Ive been looking at tech notes online. At the time my system was new late 2008 it had listed up to 1 T drives. I'm hoping to up date at least 2 drives for Storage and time machine. I did see one note that beyond 4T the screw config won't fit on the drive sleds. Do anyone have any idea and reccomendations for Size and Brand? I'd leave the two OS desinated Drives alone (Windows 10 via Boot Camp and Apple OS) and just plan on replacing the 2 remaining "storage drives" with the largest capacity that is recommended...I don't want to melt down my system...just increase internal storage vs slow usb 2 external drive access...

Here's the original 2008 drive specs

Storage

• Four 3.5-inch cable-free, direct-attach hard drive bays with built-in independent 3Gb/s Serial ATA channels; four internal hard drive carriers included
• Up to 4TB of internal storage3 using hard drives in the following capacities:
• Hard drive bay 1
  • • 320GB Serial ATA 3Gb/s, 7200 rpm, 8MB cache
    • 500GB Serial ATA 3Gb/s, 7200 rpm, 16MB cache
    • 750GB Serial ATA 3Gb/s, 7200 rpm, 16MB cache
    • 1TB Serial ATA 3Gb/s, 7200 rpm, 32MB cache
• 300GB Serial Attached SCSI 3Gb/s, 15,000 rpm, 16MB cache4