I think these are the best 20s for a Titan. 20x8.5 6/5.5 GM Trucks
+10mm Offset, 5 1/8" backspacing. This will stick the outside edge of the rim out 0.875" more than stock SE and LE rims, and 1.25" more than XE or OR.
If you go for the 20x10" with the -24mm offset, and 4.56" b.s. you will have to do the pinch weld mod for sure, and long term will be harder on things like wheel bearings. This is a total of 3" more than stock SE and LE, and almost 3.5" more than XE or OR.
Those 18x9s with 5" backspacing look nice. They will stick out 1.5" more than a stock SE or LE. Might need some trimming at the pinch weld. I know that a 9" width 4.5" b.s. MM 951, with 35 BFG M/T KMs, rubbed a little at 3/4 to full steering on my friend 6" PC lift. But with 1/2" less b.s. the 18x9 Rockstars might be o.k. ... if you can handle a smaller rim diameter. As much as I hate the looks and off road capabilities of big diameter rims, for the Rockstars' sizes that I've seen, the first one I mentioned is the best fit.
thanks for the help! i know the larger wheel sizes hurt off road ability but my truck is road only. i have another one to beat on off road. i would go for the 18's but the rockstars look kind off in that size to me. it may come down to price though...