Here's what I see. The shifter adapter is bolted to a steel plate. Tell me it isn't so. The shifter body is supposed to be bolted to the bosses on the tailhousing. No wonder why you are having issues.
the reason you see a steel plate is because I got a gear vendor overdrive unit attached to the back of the trans. the steel plate is the only way I could mount the shifter ( the of replaced the tail shaft section)