Yea...what you are talking about is the "dust cap" on the hub of a 2wd ranger. Behind that cap, is grease which lube your wheel bearings. Yea....YOU DONT WANT TO TAKE THAT OFF.
A: Use a spacer so your wheels will fit over the cap.
B: Machine the hole on the wheel in order to fit the cap.
If a wheel is designed for a car, usually the wheel won't fit a truck because of the "hub"/dust cap on the front.
If it helps, my brothers '01 coil sprung ranger needed a 7/16" spacer and longer studs in order to fit '01 Mustang Cobra wheels. Usually when guys put on 20's on their Rangers, they use a spacer.
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.