I trying to find OEM wheels for a 2011 Scion tC, but I had no luck. I found some Lexus OEM wheels size 5x114.3, 18"x7", is there any difference or anything I should be looking for?

 

Those would bolt up as they're OE Toyota still (so the bolt pattern and hub bore should be correct and they should accept the mag-seat lug nuts), but they are 1/2" narrower than stock. The stock offset is 39 so hopefully these are close or lower or else they will be very sunk in. If they are higher offset they may contact internal steering and suspension components. Needs more info to completely say they will be 100% bolt on.

 

Yeah, offset should match. Otherwise, you'll be wrecking tyres and wings.
Easy enough to crawl under and snap photo to see how much clearance you have on inside & outside.
Personally, I prefer to increase offset when going with wider wheels, which you're not.
So just match stock offset and you should be fine.