... Part 1 ...
Recently I received my Caroni TM1900BSC mower from AgriSupply and have made the following modifications.
1.  Replaced all the clevis pieces with a studier clevis piece.
2.  Replaced all bolts and nuts with a clevis pin and locking spring clip.  Actually 2 bolts remain, one at each end, since there is not enough room to replace those bolts with clevis pins. 
3.  Replaced all OEM 'Y' blades with duckfoot finish blades.
Below is a pic with the replacement parts on the left and OEM parts on the right.  Note - After taking this pic I decided to rotate the spring clip before inserting it.
		
		
	
	
 
Obviously replacing these components is experimental but I have mowed our pasture and so far so good.   I got the idea for using duckfoot blades from this guy:
Caroni TM1900 Flail Mower... - OrangeTractorTalks - Everything Kubota
The AgriSupply manager that deals with importing Caroni mowers is Rodney Barbour.  At my request he asked Caroni about replacing the 'Y' blades with duckfoot blades.  He reported that Caroni's only concern was the possibility of needing to rebalance the rotor.  I went ahead and replaced the parts as described above and fired it up.  There is no apparent vibration or noise that sounds like impending disaster so I am assuming the rotor balance is still good enough.
Here are sources for the parts I used.
Clevis (also called shackle)
SHA38LRBT 3/8" Bolt Type Safety Shackle  | GME Supply | GME Supply
Here is the post by TDVT who first reported about this model of clevis earlier in this thread: 
http://www.tractorbynet.com/forums/...alk-flail-mowers-post3900714.html#post3900714
Duckfoot blades - Flailmaster DFM-2042
SINGLE PIECE BLADE - DANDL FLAIL
Any blade you buy needs to have a 1 inch tall slot so it will fit onto the clevis.  I had to do a very modest amount of grinding on maybe half of my clevis pieces so the clevis would fit through the blade slot.
Clevis pin
Clevis Pins with Holes - Pivot Point
I bought part CP-178.
So far I have not had any problem with grass wrapping around the extra length of the clevis pin.  But if I was doing it again I likely would buy the next shorter length.  Keep in mind that the pin needs to be long enough so you can easily grab onto the spring clip.
The Caroni bolts are metric grade 8.8 which is about the same as a SAE grade 5.  I asked pivotpins and they said these clevis pins are grade 2.  Time will tell if that makes any practical difference.  We will not know if these grade 2 clevis pins work for mowing brush and rocks until someone tries.
Spring clip (aka Bow tie cotter pin)
https://www.pivotpins.com/products/bp-bow-tie-locking-cotters.html
I bought part Bow-91.  Note that this clip has a locking mechanism.  The metal is spring steel.
This spring clip can be inserted into the clevis pin two different ways.  After pondering this I decided to always be certain that I inserted the spring clip with the body of the clip between the clevis pin and the rotor.  By doing it this way I believe the odds are quite low that debris will cause the spring clip to open and fall out.
To remove the pin I rotate the rotor so a set of mounting tabs are facing me, pull the locking part of the clip toward me and pull down with the other hand.  The clip comes right out.
My towing unit is a Kubota 
L35.  This is a backhoe with bar tires that can double as a tractor, instead of a tractor that can double as a backhoe.  The engine is 35 hp with 26 hp on the PTO.  It is *not* HST.  I was a bit concerned whether this would be enough PTO power for the Caroni 1900.  I can now report it is ample.  But keep in mind that I am mowing grass and weeds, not brush and rocks.