I know there are a few threads already talking about this but what is the best specs for aftermarket wheels for the 350 F-Sport RWD?

 

Depends what you're looking for and willing to spend.
A lot of folks go to a 19 inch set of wheels from the stock F Sport staggered 18's.
19X8.5 front +32 or +35 offset
19X9.5 rear +38 or +40 offset

Some folks go with a wider staggered 18's.
Some go with squared setup...all rims and tires the same spec.
Then there are those crazy bastards that shoehorn 20's on there lol

Then you have to consider where you want to be on height...stock, slight drop, air, etc.
Check out the Wheels thread in the main forum for 88 pages of rim and tire **** lol