Tire size with Columbia rear end

[flathead47]

I have a Columbia rear end to install in my 1947 Ford convertible & want to put radial tires on the car when I do the install. It has a 3.78 main gear. The car currently has the stock 6.00 x 16 inch bias ply tires. Is there an advantage to changing the rims to 15 inch as came on the Mercury's in 46 - 48 with the Columbia. I would like to run a little wider tire than stock. What rim/tire size are you using & what are your recommendation's. Thanks for your input