I tried sockets and wrenches. The motor mount bracket on my series III looks different from the series II in the video. The area under the balancer isn't open, the metal wraps around the side (front) just enough to obstruct the rachet.
Good news is I found some 15mm 1/4 drives online, so I'll order it and get the last bolt in when I do a suspension overhaul later.
FedEx dropped by with 4 big ass boxes today. Felt like a kid in a candy store