Make sure to measure your car on a full tank of gas. Look at how much space you have when your wheel is fully cranked one way or the other and measure the distance between where you want your tire and the lip on the inside of the back wheel well you want good clearance if you are getting bigger tires if you cut it close you will be garbleing up your tires faster than you know
I like the chrome. With 20's really check the front wheels and how they turn my buddy has rubbing problems with his 20's. What if you did 19'd front 20's rear? I got 14's and 15's on my 70 you can take a look. Yours looks nice with the bigger rim i say
Just make sure the wheels have the correct offset. For example, I have a 99 Cobra and a 70 Mach 1 and they both have the 5 on 4.5" wheel bolt pattern. The Cobra has a set of American Racing Torq Thrust II's, 17x9 front and 17x11 rear. The 17x9's will not fit on the front of the Mach 1 because they have 6" back spacing. The wheel hits the upper control arm near the ball joint. AR has changed their wheel line up since I bought the Torg Thrusts. They now offer the AR-505 with 4.5" back spacing and the AR-605M with 4.75" back spacing for the earlier model cars. Both of those wheels look very similar to the old polished Torq Thrust II's.