Wheel Backspace

[hollywood1336]

I'm trying to determine backspace for the wheels I am going to buy for my car. Can someone tell me what the track width is for a 1968 Charger 318 with front and rear drum brakes. I have seen dimensions on the net for the front at 59.5" to 59.9" and the rear is consistantly 58.5". I am putting the Bill Rielly (Alterkation) independent front suspension in the car and the track width for his set up is 61.5". I am putting 18 x 8 wheels up front and 18 x 9.5 wheels in the back. Front tires are 245/40 R18 and rear are 285/40 R18.
I have an 8 3/4 axel in my car with the 741 carrier, the measured track width without the brake drums is 60" so this does not jive with the internet dimension of 58.5".
I currently have 15 x 8 Centerline wheels on the front with 215/50 R15 tires, the backspacing on these wheels is 3". If the track width is 59.5" I can calculate what I am going to need but as the rear axel didn't match the internet dimension I'm a little gun shy.
Any help would be appreciated.