if you are not going to lift I would probably go with 265/60 they are larger, but not so large as to cause clearance issues. the 265/65 would probably work depending on your wheel, but would make you trim more, the taller tire is going to give you more sidewall flex too especially if you go with a T speed rated tire. an H is what isuzu calls for and is factory, that will have a stiffer sidewall for cornering. sadly its tough to find tires that size with an H speed rating. the only one i found that I liked was the goodyear fortera tripletred. they cost an arm and a leg though

as for your wheels....

factory wheels are as follows
178mm wide. 127mm from inner lip to hub (protrusion into the wheel well) 51mm to outer lip of wheel

on your 9 inch wheel it will go...

0 offset - 114mm inner lip to hub... 114mm hub to outer lip

+12 offset - 126mm inner lip to hub.. 102mm hub to outer lip

+25 offset - 139mm inner lip to hub.. 89mm hub to outer lip

+30 offset - 144mm inner lip to hub.. 84mm hub to outer lip

so the +30 offset will get you as close as possible to factory offset LOOK but they will stick into the fenders much farther than stock, may cause rubbing issues on the inside of the fender/control arms, i havent looked closely at that area to see what kind of space we are working with.

the +25 offset would probably be my choice, its a good "centered" wheel as compared to stock. a little farther into the wheel well and a little further out of the wheel well. if you go this route make sure to test fit before driving too far just in case there's any contact in the inner fender well. they do stick into the fenders about 12mm farther than factory

the +12 offset i know for sure will work with some trimming. the numbers are very close to 8" wheels with a 0 offset (101mm inner lip to hub, 101mm hub to outer lip) which is what i have. so check my gallery for an idea of how they would look. my tires are 285's so they stick out farther than yours will by about .25" (although the wider wheel may negate that, and you will probably look very similar to what you see in my gallery)

the 0 offset is going to stick out way past the fenders.. this will require a lot of trimming, but in the event of an accident will allow you to drive over vehicles instead of running into them