From what I can gather on TB, the older V4 and V4B heads had bigger transformers and ran a little more headroom than the modern V4BH that I was referencing. I was using a '72 vintage SVT 810 cab with the 25w CTS speakers. The V4BH seemed to have a little less to give than most "100w" guitar amps, like my old DSL100 for example. I'd expect a healthy vintage V4 to run a little more headroom than my V4BH if I can trust TB. 
