In my humble opinion, I wouldn't worry about Ackerman. If you've missed lining up at the center of the rear axle, it won't be by much and the miss will be handled by the carcass of the front tires (tire slip). Many race cars run negative Ackerman and they make it around the track just fine, although Carroll Smith did say they were a bear to push around a corner by hand.

Don't know about the Nova cylinder. You might give a call to one of the aftermarket suppliers like Master Power Brakes, Stainless Steel Brakes or Baer.