2nd Gen Mini Tub Backspacing?

[TransAm400]

I'm in the middle of putting the rear suspension together but I need to give the wheel builders specs on backspace now.

1979 TA stock width rear, DSE tubs and Speedtech Torque Arm. Will be running a 18x12 with a 335/30. Fronts are 18x9 with stock subframe. Surely somebody is already running this set up and knows the backspace measurements. Any help?

[70UglyBird]

Can't help you buto what size tire in the front? Subscribing to see everyone how this turns out would love to run this combo on my 73.

[glassman]

I did 6 3/4 with an 18 x 12, running a 315...butttttt, mine can come out at least an inchtoo narrow. I believe u can use this sizing cause mine can come out a lot more, HOWEVER, the TA's can withstand a wider overall (track width).

Best bet is too buy your rims FIRST, get close to the size, mock up, then build your reared to suit