Whilst the Windsor heads have had major improvements over the years, so have the Cleveland heads. While the 4V is still available there are now other Cleveland style heads more suited to street use.
Look here:
http://www.chiheads.com.au/
As stated, these heads are the choice of heads for engine master challenges. You must however be practical with your choice. If it is a street engine you are building the 3V heads are a good balance between the older 2V and 4V heads.
As stated crazy horsepower can be had with very streetable engines which will run rings around a Windsor headed engine. I've seen Top of the line Windsor heads taken off a healthy Windsor block and replaced by Chi heads. No other alteration except some timing adjustments and 50Hp magically appear on the dyno report. Same day, same engine, same dyno, different heads.