Pretty sure its 5.5" Backspace (got the Prostars from a Mustang guy and that's what they use), but its been a while. I'll measure again tonight and post up if I'm wrong.
huh... well my dart wants a 4.25BS on an 8" that will give me 1.75" on either side of the rim to leaf and lip, but im going 4.5"BS so i can shim it as close to perfect as i can...