Here is what the y-blade setup looks like.  Basically, if the length was near 4 inches long, and the bushings fit the flails and had a center hole to fit a M14 (.55inches) I think it could be made to work.
		
		
	 
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Hello Farmall45b,
Mconnel Flail Mower is part of the Alamo group now
if you were not aware of this.
In order to contact Alamo Industrial you need to 
contact one of their regional sales managers to 
obtain parts if you want replacement hammers 
for your mower.
About your desired Y blades grass slicers;
please contact flailmaster by phone and explain
that you want to mail a worn out hammer that is 
still full length and properly size a Y blade pair 
for each hammer in substitution of same.
It would be simple enough to substitute 
hardened flat washers for the spacers as 
the hardened washers will be up to the task.
I do not think think you wil have any problems 
getting hammers or cross referencing the identical  
Grass Slicers from Alamo Industrial or to replace the
 all the bad hammers by buying replacements from 
Alamo Industrial.