for the 17x8's I could be wrong, but I don't think the fronts will work if you want to have the center caps on, as the brake rotor extends too far out for clearance. If the center caps aren't an issue for you, they will bolt right up with a 5-lug conversion. But in order for you to do a 5-lug conversion on an '83 model, you will have to change over to an 87-93 spindle, or an SN95 spindle setup.
As for the 17x9's, they will work in the rear as long as the offset is correct. If you are using an SN95 axle, then they should bolt up w/o any problems in the rear. As for the front, like above you will have to change the spindle to something later model to get 5-lugs, and once you've done that, you will have to run a 235mm wide or narrower tire that is less than 25.5" tall, otherwise rubbing will be an issue.
I am getting ready to install some black 18x8 (front) and 18x9 (rear) ROH Drift R's on my '89 Mustang with the FMS 5-lug conversion rotors and axles. Tire sizes are 235/40/18 (25.4" front), and 255/40/18 (26.1" rear).
I currently have an 85 LX 5.0 Notch with 17x8 bullitts all the way around. A 17x9 will definately fit without any rub issues if you have 5 lug drums in the back. If you do the sn95 rear disc kit the wheels will come out further by about .25" each side.
As far as the fronts go - 17x8s on an SN95 brake kit up front work beautifully. I even used the 96-98 spindles and it got the tire and wheel in the wheel well PERFECTLY and I have a 245/45/17 with no issues. Check out the attached pics. I can take a better shot for you if you want of just the front wheel and tire fitment. They fit inside the wheel wells very nice, not too tight at all.