Hey Don,
I was going to use the existing rubber mounts with "L" brackets, but I like the idea turning the original brackets upside down... I'll give it a try, thanks!
I wasn't surprised to find that the plate went between the timing cover and water pump. I found these sites and saw that the plates were similar and figured they're installed the same way:
http://www.campbellenterprises.com/motorplates.htm
http://www.racecarpartsdepot.com/motor-plates.html
I was a little concerned about mounting between the timing cover and water pump after reading a thread about reliability, but 74_5.0L_Z confirmed his setup is working well and reduces the "potential leak path for water into the oil". I also found this site with a 7 second mustang, so figured it was strong enough (has front and mid).
Good luck to you as well.