Check with Messicks online. I have a B2150 and mid-mount mowing deck similar to yours. I'm pretty sure I got the parts manual (pdf) from them for free.
Several years ago I misplaced the pto coupling for it. After searching for a while without finding it, I decided to buy a new one, thinking it might be $50. I was a full time employee and full time college student at the time, so I had very little time to spare. To my surprise it was about $400, which persuaded me to borrow a metal detector and search some more.
Fortunately, I found it where I had last used the loader - came to me as soon as the detector went off. A couple of months earlier I had moved the mowing deck from the house to the tractor shed using the loader. Of course I tossed the pto coupler in the loader and forgot to take it out. Next time I used the loader, I buried the coupler.
I'm not sure about the rck 60-24 but the part number for the RC60-71B is 76539-32030. They might be the same. Tractorsmart has it listed at $521!! OUCH! I may need one also. Mine is stuck on the PTO and I may have to surgically remove it.
I have a never used complete mid shaft assembly for a BX24 I'd sell.
Part # is K5371-32030
Bought it for a project I was working on for a mid PTO driven generator, part way into the project I found 2 new stand alone diesel generators for a very good price and bought them instead..
Don't know if it will work for you-
It is on the last page of the linked doc-
Still have the one I posted almost 2 years ago....
current price around $340 new.
Mine is new, never been on the tractor.
PM me with an offer.
I'm in SC so shipping cost might be a factor.