Guys, is there any place to get the 52-5140 cards for 4343's or are they totally unobtainium? I think I've searched everywhere but I couldn't even find a pic or a schematic of the 5140.

I got two Urei 5235's today, one was equipped with 51-5333 (18dB, 800Hz FFBREQ for 2380 series horns), the other one has a 51-5232 (18dB, 500Hz CCBREQ for use with 2360 series horns) mounted.
Can I convert one of these to 52-5140?