Rear tire clearance

I'm narrowing a 9" Ford rear end to put under my 56 Chevy 4 dr station wagon. I'll be setting the car up with a 4 link and coilover suspension. The wheels are 12" wide x 15" with MT 16.5 x 15" cheater slicks.
How much tire clearance should I build into the car? Wheel well side and frame inside clearance as well. I'm thinking of 3 to 4" all the way around in case I ever want to change rear wheel and tires to another larger size.
Any ideas will be appreciated. I am doing all the work myself in my home shop so no issues with dealing with a 2'nd party to do the work.

 

I think you wanna put this in the general section. You are in the intro section. So welcome from sunny San Jose Ca!

 

Rick,,,This is wrong forum page to ask questions,,This is the INTRODUCTION forum page

 

Also good luck with the project. I'm sure you will get some good info here.