imagine if you were 4wd. mine hit on the passenger side and the drivers side AND have been replaced once cuz the front driveshaft yoke took a chunk out of it. Get em hot, get the truck on a lift and do as Flyer says...use a fitment tool. A 2X4 works well too. I actually took my driver's side off and dimpled the area around were the u-joint is.

 

i have the dynatechs with cats and y pipe with corsa exhaust and mine started rattling/tapping under the passenger floor and i loosened where the corsa hooked up and pulled down on it then tightened it back and it quit... its a sound that will drive you crazy!!! it took me 2 weeks to find it!

 

I have the dynatechs in a 05 5.3 chevy, no clearance problems nor rattles after a couple thousand miles. The passenger side is close, but not hitting.

 

I think mine only touch when I am really torquing it. A set of urethane motor mounts might help but I don't believe they make them for trucks?