I contacted Barton last week about buying Harland Sharpe rocker for my build. He gave a very long reply. The Harland Sharpe rocker he uses are done to his specs or design. He informed me that it takes a lot of machining to get them on. Offered to do my heads for them at one thousand dollars, or would tell me how to do it. Told me the T&D required way less work and did not say anything about not recommending them. Of Course I do not know what he does to alter them from production to meet his requirements and have never had a set of production to try on a head. Other people seem to be running them and not talking about having to do mods.