Reinforcing the mounting arms on the 1.8L 1994-2004 differentials is a common practice in the MX5 world because Mazda engineered a failure point into the aluminum housing.
While that may not be a bad thing for a street car, it's also a cause of constant failures on vehicles built for competition. Until now, the only way to reinforce the differential arm was to remove the rear housing, weld on aluminum plates, and reinstall.
These KMiata reinforcement plates offer a bolt-on solution to this problem. The aluminum plates are 0.350" thick and CNC machined to fit perfectly into the recessed areas on the sides of the arm. The inner lip of the plates insures a snug fit that reinforces the entire inside of the casting. Just use a transfer punch to mark the two drill holes and then bolt them on. The counterbores are machined at an angle so all hardware sits flush against the plate despite the tapered shape of the arm.
If you're not a fabricator, this is the easiest and most affordable way to strengthen your differential housing and eliminate a common failure point.