I would like to get a sleeve hitch for my 420 tonise a Brinkley plow but having a hard time figuring out where to find one and what I actually need. Any help would be appreciated. Apparently I’m not doing very well with the search function here.
It's funny that you mentioned a sleeve hitch for a 420 because I was thinking of making one for the 420 I had. It wouldn't be very hard to build. It would be easier than building a 3ph. You just need to make the "U" shaped piece that goes where the 3ph arms mount on the axel wheel bolts and then weld and arm with the right size hole in it onto the middle of the rock shaft for the raising and lowering rods. Once you have that combo then just weld the vertical tube on the "U" at the rear and you have a sleeve hitch. You will need the "Elephant ears" that bolt onto the axels for the arms to pivot in. The only costly item if you do make them yourself are the ears which run about $80 on eBay. Since they will not be subjected to the loads of a 3ph you can make them a little lighter.
If you're looking for a cheap way out then your sleeve hitch plan may have some merits. However, the machine was designed and intended for use with a 3pt hitch, a far superior means of attaching implements. Also, although there are many, many attachments available for a sleeve hitch they are nowhere as robust, varied, or capable as those attachments designed for the 3pt hitch.
I used a sleeve hitch for almost 40 years on a couple of tractors, including an X580. The 3pt hitch was a primary factor in my recent upgrade to my shiny new X738. I've converted all of my attachments for the 3pt hitch and will never look back.
Here's a picture of one and it looks really easy to make. One piece of angle and two flat bars bent plus the cross member and tube and you're done. The second one is available from many sources and could easily be converted to a sleeve hitch. Just flip it around and put the tube on the back side.