having trouble still on trying to build the truck i want at dodge official site. here is what i want and having prob. with. it is a 2012 ram 1500 express regular cab, 2wd., i wanted the e.v.i.c. you guy's told me i had to add the trailer brake control unit to get that, i did and it worked, thanks for that. next i wanted to add the 392 reaend ratio and the anti spin rearend axle but when i click on them to add it doesn't and the 392 ratio has an ! beside and the footnote for that is requires change in selection which is where i'm lost at. can you guy's help me with this too?