I need one about 3 1/8” from the base to the flat( not including the stud). Here is my problem with the repop Mount.
your straightedge is coming off one point of the replacement mount which is adding to the height difference your seeing /measuring. they are also do not appear to be parallel to each other.
have you tried going 90 degrees with the straight edge across both mounts and or clamping the two mounts together?
I 'm going to guess the original has shrunk and it may have conformed to it's placement over the years as it appear to be at an angle.
Can you use the old mount?
Another thought may be to heat the new mount, place it in a press and leave it till it cools. Might be a trial and error process
