I briefly hooked up the 35 batteries in this box to my laptop and all of the BMS boards worked and reported that the batteries are within +/- 1mV of each other. This is great news as the pack won't need to spend very long balancing after the initial charge. I was just able to get started fitting BMS boards to the second pack before sunset, which I should be able to finish tomorrow.
Next step is to fit the second box under the car, connect all the cat5e cables for the BMS, connect the (comically) large power pole connectors between battery packs, and finish the 12V wiring to the BMS controller. Ideally I'll be finished by the end of the weekend, given the wrath of Murphy doesn't come into play to a huge degreee.
That's it until tomorrow, when hopefully I should be able to charge the batteries for the first time.