What backspacing for 18's on a 67?

[Porterbuilt]

I am looking for a little help on determining the right backspacing for my 67 camaro. I would like to run 18's all the way around. It has DSE 2" drop coils up front, and 2" drop springs in the rear. Is anybody running this set-up or KNOW EXACTLY what I can run without rubbing? Of course I want to go as wide as I can in the rear without any chance of rubbing.

[ItsA68]

18x8 w/ 4.75 to 5" bs in front, and 18x9.5 to 10 w 5.5 to 5.75 bs in rear seems to be the consensus from the threads I've read.

[D Rock]

I play to go 19x8 with 5" bs up front and 20x10 with 5.75" bs in the rear. Got the wheels just have to get the spacers cut.

[ItsA68]

why spacers?

[D Rock]

I have corvette C5 offset wheels.

[redbull396]

I have corvette C5 offset wheels.

What size spacers and where are you getting them from?