17" Wheels on a 69 Dart with Stock Suspension

The thing I'd be worried most about is whether or not the 7.25 can take a larger moment of inertia coming from larger wheels and tires. You may want to consider bumping up to an 8.25 or 8.75 rear unless you baby that 7.25 as much as possible.

You don't have many options for sbp 17" wheels, but Motech performance sell Streeter wheels ( http://motechperformance.com/product/ ) and Coy sells some sbp wheels as well ( http://www.coyswheel.com/coys.html ). They'll fit under your car, but I don't really see you getting much more than a 225 series tire under there.