Nice mid mount blade. I've got the same one as well as a rake. I hope you find out how to attach it as I am missing the same parts as you are. Here are the parts that I have maybe it will help you to figure out what we are missing?
Okay. I am getting a better understanding of this now. In the 4th pic that shows two frame pieces bolted together, the piece on the left is the rear section that mounts on the transaxle ears. The piece on the right has mounting holes on each side for the lift lever unit. Each tool (rake/blade) bolt to the piece on the right from underneath with the center bolt/nut and the outer openings are for angle adjustment.
Your pics helped a lot, Husky. Thanks.
Maybe wilberj will be asking for measurements of that piece on the left that looks similar to a sleeve hitch. :)