SOLVED!

I connected the round motors in Bipolar Series fashion using a 1.7K resistor. The 1.7K figure is a sum of the motor's current, multiplied by 1.4, which is common for a 6 wire, full coil motor converted to a four wired hookup. That resistor value, plus the wire color information found here made for another easy G540 based build-out. Thing's a champ!