A forum member's near mint pair of LX-5 crossovers gets all binding posts upgraded, outputs using current JBL parts, and inputs with PE #091-622 big boys.
Input mounting holes were enlarged, and then hand filed to create anti-rotation keyways.
Existing internal input connection terminals attach with screws to drilled binding post solder tabs.
Call it a "mechanical" upgrade, if you want humongous inputs, it can be accomplished. These'll now take up to 1/4" cables....