My vote is for shearers. I'm running r2 pipes on mine but I could be missing out on some HP. The guys who build and tune these motors swear by shearer. That's what I would go with.
mike i have an 85 frame ill sell you for 6000. they came out with a-arms fist then went with j-arms and later back to a-arms. the vin was sand blasted off but trust me!