It will fit. You are going to pay a pretty penny for a LR rim. Just so that you know, an 18" rim from a BMW X5 will fit. This is a cheaper route, in case it matters. It's cheaper because it's much easier to find X5 rims on Craigslist or at used wheel/tire shops as opposed to LR3 rims.
I have 4 MT/Rs mounted on the 18" LR rims and one BFG Long Trail tire mounted on an X5 rim as a spare. The tire/rim combo, mounted and balanced, cost me $100 (I think...it may've been $150). Since I bought the road hazzard insurance on the MT/Rs, I need only get back to my nearest Discount Tire and I'd get a new tire and be good to go again.
Just another option for ya.
Oh...the full sized tire will fit. An oversized one becomes difficult and you'd have to deflate it.