What is the proper belt size for a Wheelhorse 417-8 that goes from the engine to the mower deck?

Hi,
There are Assemby Drawings available(that is what Toro calls them) at:
https://lookup3.toro.com/partdex/index.cfm?xCaller=Toro
And just enter 417-8. Made in 1985 and 1986.
As for the deck, it was added to the machine; two or three were available for the machine. It should have its own model number.
Peace,
Clarke