Suggested wheel size for rear

It depends ENTIRELY on rearend width, spring location, and wheelwidth and backspace, what ill fit.....and what won't.
Narrowing the rear, and moving the springs, we have no idea what might work. Those measurements will be your job.
Do some research. Find out what the backspace is on the wheel you want, decide on the tire size, narrow the rear to fit.
(I'm assuming an 8 3/4)
Or..... get a tire and wheel that fits the car as is.