Hmmm. Those are shallower than I envisioned them being.
BB6P says that's 1.175 cu.ft.
How 'bout making mini-Altec Model 19 style outta them using JBL components?
Soon as Giskard suggests the best woofer to use, we'll get moved to the new DIY forum.
Any of the new PT-F waveguides will fit in the top box, and there's a variety of driver choices, depending upon how much you want to spend, for a two-way.
Alternatively, standard L-100 family M/H components would fit there for a three-way design. Plenty of those around, though they're getting a bit pricey, themselves.
Can you build crossovers given a schematic?
I'm having difficulty coming up with a decent tuning using L100 woofer (blue), tho 128H (orchid) or 2214 (black) will work, it appears. Hard to get big bass out of so small a box, but they can probably be configured to sound pretty nice....