More 904 Q's

Ok so my questions are... Running 904 behind fresh .60 over 360 and after a couple of weeks of sawing off a tire or two ,second gear started to fade away. This did not surprise me to much. Forgot to mention a new 2800 stall converter as well. The trans is dated 69 don't think it has been cracked into yet, have t-2 kit and am planning on parts from TCS products in Langley van. Yes the questions are coming.... Is it possible that my kick down linkage not properly install or adj could have caused this and if so how exactly does it work? Should I be ordering other parts with rebuild components? 4.2 kick down lever not sure what or how it changes performance, I will most likely be doing rebuild my self in the next month or so! I did shorten and grind down opening in throttle part of linkage to clear air cleaner, but have since noticed it was not enough, I will now have plenty of room with scoop install, is it worth changing to cable set up??