J-T,
My 1950 is stripped to it's frame now, so I was able to check it's dimensions and compare them to your sketch.
My Jeep has really good frame horns, and in fact the front bumper was still riveted to the frame, (4 rivets each side) so I believe it was original.
So, what I found on mine was the overall height at the front was 3-3/4" (which does not agree with your sketch dimension of 4 inches...I will also say that my frame does NOT have the small depressed corners shown in your sketch either.)
My rivet holes are also closer to 7/16" in size on my frame.
The top flange width at the horn end is 1-7/8" on my frame.
The bottom flange width of the horn end is 2-3/4",
and the outside height of my frame horn (as measured 8 inches from the front) is 2-15/16" which closely matches your sketch of 3".
If you'd like me to take a picture of my frame horns, let me know.
Dave