I ran 275/60r15's Comp T/A Drag Radials on cop wheels on the back of the last Dart I owned. Yes, they will fill out the wheel well, and with you having an E-body width, it would have to sit high in the back. However you said you already had that size of slick in the back?
As I posted a few pages back, I went with 235/60r15 MT ET sTreets for this Duster. This Duster sits a little lower in the back, and I'll be running a B-body rear end. I think it will work out just fine.[/QUO