We've used a lot of them over the years. The 440Source kits are a very good deal if they have exactly what you want. If you want a different compression ratio then you might need to mix and match parts. If you're building a race engine then you might want to use different parts. All depends what your needs are. Sometimes we use Molnar cranks, sometimes SCAT. Just depends what the customer's needs are and how big his budget is.