All the systems come with aluminum base plates. There is an optional steel base plate if you have 1" lift or want to weld supports etc.. We have sold over 800 sets in 21 years with no real failures. Some people have 30,000 miles on them. I have recently seen a few heads that had the spark plug position slightly relocated. I had offered to CNC modify the base plates at no charge, but never heard any more about it. The system is designed to fit most heads with no modifications, but won't fit stock valve covers.