I'm partial to 265/65r18 I would stick to around a 0 to +12 offset (mine are +12 and sit near flush) assuming you gonna be staying on stock suspension for awhile
I lost about 1-2 mpg from what I can tell and it was well worth it. The 10 ply tire is over kill for the taco....but I had big diesel trucks before this and am used to a firm ride anyways