1965 Barracuda MC conversion to Dual Resevior - Push Rod Question

I purchased a 73 dart mc for manual disk/drum. Unfortunately, it did not fit. It did not completely cover the hole in the firewall. the shape of the part that goes against the firewall is different than the original. I did not notice the difference in the Cardone picture but it is there. Pictures attached. I'll find one that is the same shape. It also is not come with a rubber push rod retainer. I guess it is not a big deal because the brake pedal will not allow the rod to come out of the m/c.

My picture files are too large to post. They show a notch in the m/c firewall plate that does not completely cover the hole in the firewall. I'll keep looking. Thanks.