Mark, thanks for sharing
I like this forum a lot because there is such a wealth of knowledge.
So I just went out and took some measurements, and photos.
The flywheel is 7/8" thick, the bell housing is 6" deep, there is 1.5" of space between the top of the pressure plate casing to the bell housing tranny mount plate. And from the block plate/saver plate, there is 4" and 3/8th to the top of the pressure plate casing.
You can see in the first picture, which have the McLeod fork bracket set up, that there is no room to put the fork in the there, and have it move. In this picture the bracket is more towards the middle of the housing of course (optical illusion).
Second pic, you can see the Kirkham fork installed like it is supposed to be. It is hitting the bolt on the pressure plate, which in return prevents the bell housing from being bolted down to the block (flange of the bell is 1/4 to 1/8th from contacting the block/saver plate).
Here is the whole package. The reason why I am leaning towards a pressure plate height issue is that the Kirkham arm is meant to be closer to the block (in the bell housing) so it can pivot better, and also so the push rod can actually contact the slave cylinder...
