I had a McKee 720 double auger blower for years. I think it was 86" wide. I used it on a Nuffield 465 which had about 55 pto hp
Certainly you don't need a cat 3 shaft for a 520 especially on a Belarus 400.
The blowers were made in Canada by the McKee brothers
They were sold under a number of brand names besides McKee Snolander including John Deere being one of them and also Kubota both from the 1970's.
I bought many parts from John Deere.
I recommend a shear pin pto rather than a slip clutch and in that way you don't have to worry about the clutch getting seized plus the shaft will be cheaper.
There is a shear bolt between the chain sprocket and the cross auger. If I recall it is a grade 5 5/16" carriage bolt.
To get your pto shaft I would go to a farm dealer armed with lot of pictures of the pto shaft on your tractor and the input shaft on the blower together with a measurement of the shaft diameters.
The length of the pto shaft is critical. Too short and it will come apart and too long and it will bottom out putting great strain on the back of your tractor possibly even damaging it.
You could possibly build up one cheaper at TSC but since your are new to this I would think the dealer expertise would help besides they may even have used shafts.
The shafts should have a plastic sleeve or if an older model metal sleeve over all parts of the shaft to prevent entanglements. For these sleeves to work properly they should have a chain on either end which is fastened to the blower frame.
When the metal pto shaft is turning, the out plastic/metal sleeves will be stationary.
Here is a video showing how to cut a pto shaft to the correct length produced by
Tractor Attachments And Skid Steer Attachments For Any Tractor Or Skid Steer
https://youtu.be/0vBFJcvs5SE
Dave
M7040
