Need wheel info asap !!

I know I'm beating a dead horse but im having trouble understanding this whole back spacing thing. I'm currently running 2nd gen sport wheels w/ 285/70s on my 03 dbl cab w/ 1.5" spidertrax. Clears perfect around 1/2-3/4" between tire and stock UCA no running anywhere. I really wanna put aftermarket wheels on and keep my tires. I would like them to stick out a little bit not to much tho. From reading on old posts and doing my calculations if I go with a 17x8 wheel and my 285s I would need either a 3.75 or 4" bs without spacers correct?? If not please help, I wanna order wheels this week.! Pics are appreciated !

 

Did you try this calculator? http://www.rimsntires.com/specspro.jsp I'm looking at a similar issue with debating a 8.5" or 9" wide wheel. This may be a thing that you just gotta try it to see.