If you shy off from the purchase l think we could get very close to the stock 3143 crossover
It actually doesn’t use tapped inductors.
All you need is to come up with a foil badge and l think that guy on eBay could be pursuaded to make some of those.
The actual electronics is a weekend job on the work bench with a soldering iron.
The metal enclosure could be fashioned from sheet aluminium and painted grey
I actual did a 3143 charge coupled design for a member last year.
The stock schematic could be laid out very close just like Jbl did (non charge coupled)
You could do the same with the rear plate
The Biamp switch is a multi pole rotary switch. They can be sourced.
If the stock box is in really good condition then that’s a win.
Something to consider before you pull the trigger