Using vacuum gauge to tune engine?

You’ve made a bunch of changes to the engine. That cam if I remember is around 241degrees at .050” it will be some what choppy especially in a 383, the vacuum will fluctuate some. How did you set the preload on the lifters? Hot cold. The aluminum heads have a different growth rate than iron. There shouldn’t be lash with hydraulic lifters, they should be preloaded and I believe I hear lifter clatter in the video.