Looks like I screwed that purchase. I haven't been able to find any premade boards that accept these, let alone an Arduino shield that accepts them. All of the RS485 shields I have found only route the TX/RX lines to pins 0 and 1. That doesn't help me either as I'm either using a Mega and Serial 1 or Nano/Uno and a software serial port.
Well, I'm off to go build another shield.