I know this is slightly larger than your setup would be but - my
M6040 is rated for a bb not to exceed 72" wide. The Kubota dealer set it up with a Land Pride RB3596. I'm sure this setup does not exceed any weight limits and I've never had a moments problem with the 24" extra width. Its almost 100% use for clearing snow off my driveway. Strange, but the specs listed in the Land Pride Op manual would indicate that the
M6040 is well within limits for use of the bb. Could be the implement mfg wanting to sell more bb's. I see no way I could clear snow effectively with a 72" bb. With the 96" RB3596 angled and offset so that it effectively clears snow - it JUST clears a path a little wider the the back tire width. Back tire width - 80 inches.
BTW - lest we forget, welcome to TBN. In my 32 years experience with my mile long gravel driveway - a back blade (bb) is not a really great implement for grading a driveway. How do I know this?? After that period of time one would think sufficient skill had been learned to efficiently use a bb to maintain a gravel driveway. Well, in my case it just didn't happen!! I found that no matter what I did the bb will follow the contours of the driveway and will not level out the driveway as you would like to have happen. I finally got a Land Pride Grading Scraper and Waa Laa the driveway is almost good as new.
Even my bigger tractor, at times, has trouble plowing snow. I've learned - just back off and take a smaller bite. Deep, wet snow can be a real load for a back blade.
If the bb you are looking at is in good shape - the price is certainly good. I would buy it.