This site
http://gtc.org.uk/resources/mountings/mountings.asp gives specs for a lot of the commonly used tripods and heads. I did a little write up on pros and cons of different heads I've used a lot (Sachtler 18,20,25,20Plus,25Plus,Ronford Baker 2004,2015,Atlas30,O'Connor 2060,2060HD,2575) but I can't find it now!
Any specific questions?
Steve