Hi Lindy
Your shifting problem looks like a tired clutch control symptom! Is it easy to shift when your engine is not running?
About the toploader, I would like to relate a desaster that appears at the last "Le Mans Classic" to the Mustang "Hertz" (see pictures here attached). Toploader gear boxes have very strong reputation in muscle cars and it is very rare to see these kind of damages.
I thing that the problem origin is the conjonction of 2 successive troubles.
The first was the disconnection (for unknow reason) of the connecting rod to shift the 3 and 4.
The second was the excess wear of the locking device balls that are in charge to avoid to move the 1/2 fork if the 3/4 fork is not in medium position (and reciprocally).
My feeling is after to broke the 3/4 connecting rod, the driver has tryed to shift to the second or the first ratio. As the locking device was not working, he has shifted the first even the 3 was locked. Pictures shown the result
