The minimum with rim for a 205/70-13 is a 5.5" with rim,(6" optimum)
and thing smaller and : 1) it would bulge the side walls making it squirly as hell, 2) higher risk of blow out due to strain on the bead, and 3) it would look like sh*t....
I am running a set of Cooper Cobras 205/70 -13 on 13x5.5 rims and it works great.
Most alloys have the size listed on the back side of the rims, as to the steel, I am not sure but they look like around 4", but dont quote me on that....
A 205/70/13 tire I would have to say would be way to tall for the car. You'd look like a mini balloon tired 4x4 not good. 205/60/13 will work on the stock rims without any ill side effects . I've been there done that long time ago never had any problems. 195/60/13 would be about the best compromise on stock rims if you're worried about it. Cooper tires has just about any size in 13 that you might want even a 165/80/13 they even have a 155/80/13 not that i'd recommend either one but they have them if you want them
I used to run Falkin's on my Porsche 914 when I had it. I agree that they are not as grippy as some tires out there for all out abusing but, I found them a good overall street tire. Good wear, good wet traction.