Hi Chad,
You can use multiple DeckLink 8K Pro cards, but you would capture as seperate input streams each with its own IDeckLinkInput/IDeckLinkInputCallback object. Normally for 3D capture, the left-eye and right-eye frames are both received in IDeckLinkInputCallback::VideoInputFrameArrived callback.
If your camera sources are locked to common reference, then you can implement Synchronized Capture feature that was added to Desktop Video in 11.0. This feature allows grouping of multiple inputs to sycnhronize the start/stop capture. This feature will allow you to align the left/right eye frames based on the captured stream times. Please refer to section 2.4.13.1 of DeckLink SDK manual for more information on Synchronized Capture.
Multiple streams of 4K DCI 444 120fps will require
significant bandwidth and you will need to make careful consideration with the PC system requirements for your application. As a starting point, please refer to the following support note for guidance:
https://www.blackmagicdesign.com/support/note/9568.
Regards
Cameron