I am using risers for the fat bars.I ran a 62t factory pipe manifold on a 61x cylinder in the past. The only difference I could see was the bolt holes were larger. Not sure if there is any difference in the exhaust ports between the two. If you call the Pro Tec tech line they are extremely helpful.
Were you able to find risers for your B1? I'm looking for some as well to use with 7/8" Blowsion bars.