Getting to Mojave, updating of firmware to 5,1

Plan to update my early 2009 Mac Pro (4,1) to Mojave install level — Xeon X5675, 6 core processor and a Metal capable GPU.

To start the process, I need to flash the firmware. Currently have a ATI Radeon HD 4870 512 MB installed (EFI capable), but not sure if it is an Apple card or just a flashed Radeon. Should I find an old Apple card and stick it in the CPU or give it a try with the current card? And, what will happen if it is not a correct card?