I'm a board member for a local cemetery assoc and we recently retired our Excel 260K and replaced it with a new Hustler X-ONE with rear discharge.
I have in my documents a pdf of the operators manual for the 251K and 260K models. It is 6.2 Megs in size and I can email it to you if you would like. Both the 251K and 260K are very similar and it appears that the difference is that the deck extends out the left hand side more on the 260K. I've done the maintenance on the 260K for the last 10 years and although not the easiest job, the V belts are not that difficult to replace. With the engine mounted on the deck and the deck hanging from the frame by 4 straps, removing this deck is not practicle.
I highly recommend that you use Hustler V belts on this machine should you need to replace any as installing them and getting the correct tension with the correct size V belts is easier to do. The operators manual is fairly easy to read and understand. I also have a parts manual in pdf but it only covers the 260K model however I think that the machines a very similar to each other.
I scanned these manuals from the originals and I can email either or both to you or print out a copy and mail them to you, I'm in CT, let me know. The dealer took the 260K and all the printed manuals with him when we took delivery of the new X-ONE which by the way is an awesome machine!!
Bob MacGregor in CT