Ed you will be hard pressed to find plans, there are just too many variables, Bergy's site give some detail on one.
Tower design is serious business at 80' with large rotors, many factors come into play, not the least is the anchors V ground type.
Anchor point distance from tower is very critical, guy wire spacing very much so.
I now have 3 tilt up tube towers, one commercial and two home built. Some conciderable amount of learning has gone into these two, especially the 80' which we put a 3.6m rotor on top of. I don't think we will be publishing details of that fiasco.
There are very good reasons why most commercial towers are more costly than the turbine.
I guess this does not help much but do it once and do it right, more detail is needed to offer any of my experience( ground type, rotor diamiter etc).
allan down under