Diaphragm clutch and free play

As to the casting number; No the number is on the mounting face between the bell and the trans.
The correct fork pivot will cause the fork to sit near the front of the window with the TO bearing against the PP, and as the fork moves back, it will end up near the back of the window.
The fork you have now is never gonna play nice with that tube in it's current location. I would take the fork out and make sure it is the 10.875 one
CF702 appears to be the correct one for your engine/body style and is supposed to be the 10.875 . Pull yours out and verify the length. Also verify that it is sitting correctly on the TO bearing,which being sliped into the TO bearing clips,fully engaged in the pivot, and properly located in the window.
Or you could just cut that header pipe out of there and move it over.
This is HotRodding 101.
There are a couple of forks to choose from; not all will fit properly in the window. There are straight ones, offset ones ,and about 3 lengths. The one you want is supposed to be 10.875


Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists