I haven't seen it mentioned in a while, but there are a few people out there running chevy 1500 leaf springs. They are roughly 6" longer than the ranger springs, but same width (hence using their shackles). You will have to re-locate the forward spring hangar by drilling out the rivets. You can re-use the front hole in the frame, and match it to the rear hole on the spring hangar, then drill new holes in the frame for the other bolts using grade 8 hardware. The chevy leafs should flex a little better since they are longer, but also provide 3-5" of lift if I remember right. You could also use the chevy lowering shackles for more height if needed.
You should get some lift from explorer springs too, I would imagine. Maybe slightly less since they have been holding more weight and may sag some. I would look for the ones with the biggest spring pack. Again you could also use the longer chevy lowering shackles.
2006 F150 FX4 Super Crew - Bilstien 5100s leveled 2", 35" KM2s, 4.56 gears, Detroit locker, Eaton E-Locker, Traction Bars, AEM intake, Xcal 2
2010 VW Golf TDI 6MT