Open Series Advice

Hey y’all, I’ve been wanting to run the open truck series but I’m hesitant because i always find myself doing poorly in the trucks and I wonder if it has to either do with the setup, competition or my driving. I usually drive the 87’s and the gen 4’s so I don’t really know “whats good” for certain runs like long or short and how to setup a truck. Just wondering on any advice from better oval racers than me.