Group 44, true, but I'm thinking that the angle the belt is hitting that front pulley it will wear faster than normal. If they only used one set of idler pulleys I don't see how the belt would align up properly. I'm thinking it will look like this. V
Plus that belt is shorter than a mower deck and is twisting more because the drive and driven pulleys are parallel.
I don't know, I'm just throwing that out there. I live in Georgia and have never seen a 451 or a 551.