What are you guys using with respect to the subject? The Rohn brand seems to be the most popular.

I'm looking for a self-supporting tower in the range of 40-60 foot. Let me know what you guys think; I hate to reinvent the wheel.

I'm looking for a self-supporting tower in the range of 40-60 foot.

That's utility pole size. Given the quantity of utility poles these would be more competitively priced and have a greater rang of suppliers.
http://utilitypolesolutions.com/surplus-steel-poles