Ok here are some pics. Couldn't get a pic with the hole tank and stand because right now it's sitting with the front facing a wall. But I was able to take some pics of the overflow setup as well as some equipment.
Here is a pick of one of the corner overflows and the bulkheads.
Above is where the plumbing starts. These were attached directly to the bulkheads. Each drain line had 1 3/4" hose and the return had 1" hose. The drain lines converged at a "T" where they then drained into this Amiracle Reef Pro Wet/Dry filter system w/ filter sock and bioballs as seen below.
The water entered the left side into the filter sock, there was a pump inside this compartment which pumped water up into this protein skimmer. The water ran over the wall and through the bio balls, through the filter sponge and into the last compartment. There is a bulkhead here where the return pump was attached to pump the water back to the tank as seen below.
Clearly the pump is not attached but you get the picture. This was how the guy had it all setup. Obviously this is an older setup. Ignore the equipment in the last compartment, it doesn't go there I just had it there for storage. Now I'm not too interested in using this setup as is. I haven't heard good things about bioballs, don't like the filter sock, sponge filter, and not too keen on the protein skimmer. Now you all have seen the sump/fuge that I have already built (but still leaks). Here it is again.
Reminder that the protein skimmer was going in the left, return pump in the center, and fuge on the right. Now here are my initial thoughts on all of this. The 29 gal sump/fuge is a little on the small side for the 125 gallon tank I just purchased. So to get the adequate amount of flow I'm thinking about using both the sump I built and the Amiracle filter system. However, I won't be using the Amiracle as it was designed. Initially I'm thinking about running both drain lines to the protein skimmer in my sump. Then using my mag 5 (which is not a sufficient return pump on such a large system) to pump water to the Amiracle which can be setup as a fuge. I could use the left compartment as a fuge w/ a deep sand bed and remove all the bioballs, filter sponge, filter sock, protein skimmer. Hook the return pump up to the bulkhead and pump the water back to the DT. Although having the return pump not submersed and sitting directly on the stand seems unusual to me. But that is how this setup was run back then in the pre-sump era. I'm sure you all will have interesting modification or overhauls. I'm open to all ideas. I understand that setting up a 55 gal as a sump and fuge may be much simpler. But I don't know if I should just utilized what I have or just throw this Amiracle away. Thanks for taking a look.
P.S. Here is the bucket of salt I was given.