Appropriate Wheel Offset for 18" Wheels?

Hey there, I found some wheels on CL. That seem like they'd fit on my '68 Dart. They're currently on a Mustang, 5 x 4.5" bolt pattern. They're 18 x 8's on the front with a 245/40/18 and 18x10's on the rear with a 275/35/18. The only problem is I'm waiting for a response on what offset they are. If you look at the pictures, it kind of seems like the rear wheel is sticking past the quarter panel, so it might have less of an offset. If I get these, I'd probably spend half as much than if I were to get all new wheels and tires.

As of now I don't have my front end together, but I'll be running the whole Hotchkis TVS with Dr Diff's 13" brake kit with Brembo-style calipers (I believe the center bores on Dr Diff's hubs are suitable with Mustang wheels). On the rear I've got the Hotchkis leafs, a stock length A-body 8 3/4, and Dr Diff's 11.7" Cobra Mustang Caliper kit. The whole car will be lowered approximately 1-1.5". I know it's possible with some work to fit a 275/35/18 on the back of a Dart. It might take some work (like trimming or rolling the inner wheel lip).

Approximately what offset would be desired for the front and rear?