Coug gave you the best advice!!! I use the Cranford's to start the hole and then use the cheaper steps or large hardware lag bolts. In fact, I just ordered a dozen Cranford's from Cabela's.

The trick with Cranford's are that they are "SELF TAPPING". None of the others are! Bass Pro does not carry them from what I've seen. I guarantee you the Cranfords will make a HUGE difference!

Here is the website:
http://www.ezyclimb.com/treesteps.htm