#2 double coil springs will work good but make sure the trap is equipt will a swivle and a spring on the chain to reduce the amount of strain put on the animal when they try to pull out. The spring on the chain adds a little give when they lunge and it's not such a abrupt stop when they hit the end. Don't give them alot of chain to work with either.

Coyotes are by far the toughest animals in this region to trap They are strong and if you don't use quality equipment they will get away.