What Bs?

okay all. i am just being a little lazy so bare with me please. I have a 71swinger stock suspension and wheel wells. it has a stock b-body 8 3/4 rear. i am looking at getting cop wheel from Wheel Vintiques. they only offer 15x7 with 4 inch bs. will that be enough to clear a 235/60 tire? or will i have to take the wheel to a machine shop and add some bs to it. i was thinking i need about 4 1/2 to 5" bs. what do you think?
Thanks for looking