chakka

Recently installed a new set of wheels. I see a ton on info on offsets, outside clearance, my question is, how much inside clearance do you need. What is enough? Just clearing the oil line by like a 1/2", 3/4", 1".....etc. The room inside will help me know what I may or may not need to do with the outside clearance.
Thanks!
wheels/tires are 265/35/18 MPSC's