Equalizer/Z bar length

[1/2fastback]

I ended up with an equalizer/z bar with a pile of things I had purchased, but I'm not sure if it's for an 8cyl or a 6cyl. I have a '65 fastback with a 289 block, and a T-10. How long (or wide) should the bar be from the block side mount to the inner fender mount? Thank you in advance for your help.