I'll try the blocking, hope I can get it fastenned through studs. Going through the plywood is out because there's siding on the other side.
Starting to lean towards the garage as a goal tommorrow so I can close the wall, put in the work benches and start organizing my car parts to get the project car back inside.
Please do NOT consider any "before" picture of my house as any kind of endorsement of any particular construction method. In fact, you should probably assume that if I post a "before" picture, I am posting it because I am soliciting advice on a proper replacement for one of MANY things done wrong by a previous owner.