Would my fenders survive a week?

Alright so Friday I am getting a lift put on my truck. I am gonna go with a 3" lift. Front diff, drop, and rear add a leafs. I currntly have some 285/60/18 tires on my truck, and they rub just a little at full turn. I found a set that a guy has some half worn 305/65/18 nittos that he said he would trade me and give me enough cash to pretty much pay for my lift.

Just wondering if I could get away with running that big of a tire for a few days...being very easy no hard turning or anything like that.

 

What kind of truck are we talking here? And why 305s?.. half worn...