For front implements, such as a snow/dirt blade, you will need to cut the lift paddle (that is what you have the you stated U bolts) in order to modify it. I do not know what you mean when you said the hole in the cylinder??? You should NOT have to drill any new holes in the paddle to use the implement lift. The only holes that you would need to drill are in the frame to mount the hydraulic lift itself and it sounds like you have already done that. You should be able to just bolt the lift paddle to your rock shaft bracket. I had to use longer spacers for my hydraulic lift, so I had to also make a modified lift rod that extends out, but you should not have to worry about that. Mine is because someone sold me an electric lift rockshaft, but told me it was for a hydraulic lift.
The float at the clevis allows the implement to "float" like the float button on the Armstrong lift handle. You should NOT use this with a snow/dirt blade on the front as you will want the down force in order to move the material and not float over the top of it.
If it helps, look under my profile, look in "My Album", then "My Cubs". Go to page 3 and bring up my 123 Snow Ready (1st picture). Enlarge the picture and maybe that will help you examine the set up.
or
Looky Looky at the 1st pict of this "hydraulic" lift (the seller calls it a hydro lift, but that no is correct):
https://www.ebay.com/itm/14287932031...MakeTrack=true
Cub Cadet 123