That setup would work.
However, why stick with 18" tires? They'll set your wallet on fire. You could buy 15" or 16" wheels AND tires for a comparable price (maybe even less), than just the 18" tires.
That way you'd be sure to get a set of wheels with the proper backspacing, around 4.5" or less.
Also, some of the Grapplers are heavy as asteroids...not sure about the Terra, specifically. Might wanna look into it.