Will the mighty Jet pump fit in the the back of that tank? Not sure that it will without modification. But if you can, then for the best results I think i would suggest the single 1/2in RFG. That would produce the best and strongest punchy randomized flow for the amount for the GPH that pump can deliver.
https://vividcreativeaquatics.com/s...h-1-2in-random-flow-generator-nozzle-wbfk050/this kit comes with the 16.5mm adaper that you'll need
If you don't want to run that pump at 100%, then you could also go with th dual 1/4in Kit. that would work well, and you may be able to get away with running that pump at around 75%
https://vividcreativeaquatics.com/s...k-return-line-upgrade-kit-1-2in-to-1-4in-rfg/
You'll also need the 16.5mm adapter for this kit to attach
https://vividcreativeaquatics.com/shop/16-5mm-modular-hose-to-1-2in-loc-line-adapter/
You could run dual 1/2in RFGs, but honestly, I think the result would be a bit underwhelming, since 320GPH is not really enough to get the full effect.