I don't know what Sprears is?? But I would try to replace the plumbing on the pump so it works. That actually looks like a smaller MAG to me. I am wondering if you will get enough output from that pump. What is its rated GPH?
If you change the plumbing (if that is possible) then I would ditch the unions, they just take up space. Nothing needs to be glued, so it will come apart easily. That is if this is going to be an IN sump which I would HIGHLY recommend.