Just found this EZsteer PS conversion kits on Ebay. Looks like gearbox is relocated with adapter plate. I still haven't dropped the hammer on a borgeson one because I know it will take a lot of mods to fit with my 460/4spd Z-bar installed.
https://www.ebay.com/itm/52-53-54-55-56-57-58-59-60-61-62-63-64-Ford-Mercury-Power-Steering-Conversion-/121743442899?_trksid=p2385738.m4383.l4275.c10
No experience with this one. I can tell you from personal experience the Borgeson is a wonderful kit. Absolutely no issues, a bolt in kit that defines "bolt in". Their tech support is second to non as well.
Looking at the add I see an adapter plate that would move the box closer to the exhaust. That box looks like the same GM style box Borgeson uses but the Borgeson box bolts directly to the frame and actually takes up less space between it and the exhaust (FE and 351C) than the stock 57 box.
Not sure where the fit problem would be with the Z bar? If you have the stock box and the Z bar in there now the Borgeson should be no fit problem at all?