Roberto, I can only imagine your frustration level with this problem. One thing I noticed you mentioned that these are stage IV heads that have had a lot of work done to them over the years. Have you checked to see if one head is milled more than the other? Hence the possible need for different length pushrods. I had a set of heads years ago I put on a motor and was chasing my tail on things only to realize one had been shaved about .030. I run solid cams but I could see if one of your heads was shaved this is maybe whats causing you the grief with your hydraulic cam???