Clutches are rated for torque. The HP is not important while the maximum torque is. Since "built" engine usually have the same or less torque, you can confidentially use a standard clutch.

HD clutches are rated for more torque. And will better stand up to abuse (clutch dumping). It is the clutch cover (pressure plate) that makes the most difference while the clutch disk is usually the same standard vs. HD. Use a HD clutch for drag racing or burnout usage.