The following range is perfect
11.00 to 1.00 through 20.00 to 1.00
11.00 to 1.00 can be perfect for a high hp power adder combo
20.00 to 1.00 will be seen when you let off the gas and cost to a stop
If cruising around town in your Stang and it is stock ........
You would see values in the 15's a good bit of the time
As in most things ... application matters
If taking typical NA street combo kinda situation during WOT ........
12.5 - 13.0 to 1 is a fairly safe range to be and make good power
If you were gonna be shooting for maximum gas mileage ......
You would lean it out a good bit from the WOT values above .......
Grady