When installing Flathead's system on the rear brakes it is best to also purchase what he call his "pins". They replace the rollers that ride on the roller tracks. They are square instead of round and they slide on the tracks instead of roll. Each of the four sides is off-set by 1\16" of an inch by the shaft being off-center. Each pair for each wheel are a mirror image.
The drums must be round and the shoes arced to match. You also need a centering tool (Bratton's has one for $44, part number 2695). You also need to have the roller tracks relatively flat so the pins will slide on them.
The trick is to examine the pins carefully and determine the measurment of each side and mark them 1,2,3, and 4. I paste a piece of paper on the flat side and mark them. Be sure you have a mirrored pair. It is a trial and error effort to determine which number to use that will center the assembly fore and aft. They are difficult to install because they will want to rotate on you.
Final adjustment of each wheel should have the shoes as close as possible to the drum without dragging. This why the drum has to be round and the shoes arced to match.
If you go to the Orange County MAFC web site
www.ocmafc.org and click on "tech articles" it will bring up the tech page. The two articles that appeared in Model A Times are posted there with the permission of John LaVoy. If you go to the top of the page and click on my name you will find an additional artcle that describes installation of the "pins".
I have installed Flathead's system on several cars with good results. I left the long spring off as he perscribes. I put a set on my Vic several years ago and I am very pleased with the improvement in the brakes. I put a lot of miles on it each year. Last summer I drove it to the MAFCA meet at Vancouver, BC and back to Southern California and the brakes worked very well except when they got wet in a rain storm.
Tom Endy