Please remind me, what is the intended tank size? Why a Barracuda? It is a high head pump and is not efficient for high volume low head applications. A Dart will supply only 20 percent less volume of flow for less than 50 percent of the wattage used. Your pump will not lose any pumping flow capacity from static head losses used in a closed loop situation so a Barracuda is expensive over kill. How many return nozzles will be open at one time. Hopefully at least two if your using a Barracuda as 5800 gph through a 1.5" return will be way to much velocity. It would be strong enough to blow over/down fair sized live rocks. It would definitely need at least a 'Y" at the bulkhead to reduce the velocity by running the return through two nozzles instead of one. I assume your two 1.5" intakes will join together with a "T" or "Y" fitting to feed a single Barracuda pump. Redundancy is nice. why an overflow box. They waste huge amounts of space. Have you considered a Calfo overflow or a glass-holes overflow. They work better, and quieter than standpipe overflows and do not use up anywhere near as much space.
