Ummm.... First off, the belt itself is a Goodyear Gatorback belt, isn't it?
863k6 = 86.3 Pitch Length - 87.05 Outside Measurement X 6 ribs
4060865 = Effective Length in Inches--86 1/2, Metric Part Number--6PK2195, Number of Ribs--6, Outside Length in Inches--87 1/4, Top Width in Inches--27/32
So it's .2 inches shorter than it should be? I am not sure if that's going to make a difference.
But then I look at Goodyear's webpage:
http://www.goodyearep.com/productsdetail.aspx?id=3128
4060865 6PK2195 6 86.5 87.25
where 86.5 = Effective Length and 87.25 is outside length
Goodyear doesn't have a listing for a 86.3" belt.
Can you post some pics please?