what tire size should i go for if i want to run enkie nt03 18x8.5 +38 18x9.5 +40

 

225/40, 255/35.

 

225-40-18. 265-40-18

 

225/40F. 255/35R

or 245/35F

265R may be possible but stick with 35 series if you want to keep rolling weight down and stay with stockish gear ratio.

 

How hard will it be to fit this 245/35 and 265/35?

 

you're gonna need a roll + flare on all the fenders.

 

Not sure about a flare needed for the rear. You will need a roll and run a min of at least -2.5 camber front and rear. You will likely need to pull your front fenders slightly as well. 225 up front you won’t, unless you’re dropped more then 2".

 

You are good even factored in the offsets to get these to mount without much work