I wouldn't worry about the speedo as that should be easily corrected. And I don't think they would change anything on the alignment geometry, if that is what you mean.
But, Rusty is running 31's and they rub the radius arms as you get close to full lock on turns. I think Clay is installing a lift to get away from that.
Also, you need to consider the width of your wheels vs the tires you get. I recommend going on Tirerack.com and looking at the specs on the tires you are interested in. That will give you the min and max wheel width for them, and you need to make sure yours are in that range, preferably in the middle.
Gary, AKA "Gary fellow":
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Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI