Strong vibration, front end?

Sorry to bother again! I have been able to solve all of the problems for my 96 Tahoe through this site exept this one! As mentioned I have a 96 LT 4x4, when I drive at highway speeds I get a strong vibration in the steering wheel and gas pedal. I also sometimes hear a "knock or popping" sound from the passenger side. I am getting all new rubber on it tomorrow and will have them balanced and the front end aligned. If that doesn't work, am I looking at a front suspension issue or maybe motor mounts? This truck has 115K on it. Thanks for all the help, this site has saved me lots in "dealer checkups".

Brian