You want to cut a strip of plastic where the mud flaps screws mounted the flaps...just the front wheel wells rear edge.



This is someone else's trim, but the pic was handy...

A one inch wide strip should do it, right at the edge where the back of the tire swings though on turns....I did that for 275/70/16's years back, so it should be fine for your smaller 265/70's befoe I had any lift.

I had no trimming needed at the front of the well...the vibs might be because the fenders were being strummed by the tire contact at their rear.

I have 33x12.5's on now, and I haven't had to re-trim yet. (BL+SL helped)