Dick,
I just had another passing thought about those plates. Somewhere (?) I read that those 3 screws have to be mounted in a certain order; What that order is ?? There were 2 longer ones & 1 short one.
When I was working on my `57TR3; It was strongly suggested to me by BCF memebers to replace them exactly back to where they were Orig. mounted. Reason being; If you put the longer screw into the hole that requires the shorter screw; You may pot. try and over tighten it & "Crack" goes the windshield.
Just something to consider or you may find that Thd. somewhere here? I was restoring my `57 about 2yrs ago.
LOL, Russ