That is correct. I recently ran into a problem with stroking my 4.0 to 4.6 because the fellow I bought my parts through sold me a cam for a carburated 4.2/258 instead of a fuel injcted 4.0. The only way to increase the preload on the lifter is with a longer pushrod, I have adjustables. You would do this if your rocker arms are loose at top dead center. The only way to decrease preload on the lifter is by adding shims under the pedastal the rocker arms bolt to. I believe that the preload should be between 40 and 80 thousanths.
I hope this helps, it can be hard to make sense of all this. I believe that there are some conversion kits out there to change over to the adjustable style but they run $500+. Good luck!
