You'll need to do some quick measuring of your backing plate/brake flange to see if you can use the 6,000 lb Dexter Electric Brake Assembly for 4 Bolt or 5 Bolt Flange - 12" - Left Hand # 23-105-09.
I have added photos below that I hope will help. One is of a standard 5-bolt brake flange where the bolts are 2-1/8" apart except for the bottom which are 3" apart. The other photo is of is the brake assembly which shows the dimensions of the AL-KO/Hayes 4-bolt flange, where the holes are 3-1/8",... view full answer...