Will p215/60/r14 tire fit a dart steel rim?

It will fit, but it's a little wide and will look pretty bulged-out. The standard rim is 4.5" wide, and 215mm is almost 8.5 inches. It would be a better fit on a 5.5" heavy-duty rim, or a rally wheel. I have 215/70-14 on 14 x 6 rally wheels and that seems to be fine. Most tire manufacturers can provide a list showing the minimum width rim for each tire size.