15 x 10's with a 4 inch backspace are perfect, then you won't need wheel spacers. These are American Racing Tailgunners 15x10 w/ 4in backspace with 33x12.50's.
theres not a damn thing wrong with a 4 cyl. YJ! as long as it's geared correctly you've got nothing to worry about. my 4 cyl. yj keeps up with the 6 cyl. tj's every time.