1.5 inch blocks in the rear and the front is sitting about a inch or so lower than the rear but some pretty bad vibration at hwy speeds on the interstate. any ideas?

Never started till your "lift" kit install? The steering wheel still straight after the putting it all in?

Did you get an aligment done after the lift?

The bolts on your keys aren't maxed out are they?

DEWFPO

I found on my 02 , cranked up to far that it was caused by the severe angle put on the front cv jonts, but i could be wrong. my 02 cents

I am not sure why you have that. I installed the keys and I have no vibration at all in mine... Not sure what to tell you. Get an alignment, rotate and balance your tires and then see what happens.

Did you rotate the pumpkin? The differential pinion shaft must be parallel to the transmission output shaft or you can get a driveshaft vibration (precession). I'm surprised this isn't more common on trucks with lift kits. Anyone else remember what alignment wedges are?

Didnt start until keys was installed and no they arent even close to being maxed out. I did get the tires rotated and it was alot better until the tread pattern wore back in.

I'm thinking an alignment is in order.