Wheel Issues

I have a 65 mustang that is sporting the original 4 Lug. The problem with this is that wheels and tires for it are few and far between and what I have seen I do not like. I have located a adapter that allows for a modern 5 lug wheel to be mounted on the 4 lug setup.

http://www.ezaccessory.com/Wheel_Adapter_4_Lug_4_5_To_5_Lug_4_5_p/4450-5450.htm

This adapter is 2" thick though. I need some help determining what size wheel and what backspacing will fit with this without it sticking out the fender and looking all sorts of goofy.

I would like to run a 15 or 16" wheel, but as I said I have no clue how to figure the backspacing so that it doesn't stick out of my fender.
 
You would probably be better off just swithching to 5 lugs. You can get used drum spindles pretty cheap and probably get an 8" for practically nothing too if you arent in a hurry and watch for one...
 
you should start checking out wheels for early datsun z cars, like the 240-280 series, they have the same bolt pattern as the early mustangs and you can get some pretty nice looking wheels for the z-cars. don't use those 2" spacers, they could be potentially dangerous, people use wheel spacers to put late model wheels on mustangs all the time but they are gnerally limited to around 1.25" or so, any bigger than that can be very dangerous