If it is a 01+ 4.0 SOHC, which we still don't know because there still isn't a sig or any info on the truck, the intake manifold o-rings are reuseable but it's smart to go ahead and replace them when you do it. It's a pretty easy job removing the manifold. Just take your time and unclip all the crap attached to it and it's good to go. I had to go back in and trace an incorrect solder I made...