The term "3/4 specs" is an outmoded way of identifying a fairly stout cam profile, dating back to flathead days. You would be better off telling your camgrinder the weight of vehicle, intended use, RPM range you operate in, etc.
If it is to drive a full size vehicle on the street I would imagine a duration around 265 - 275 degrees and a lift of about .500" would do. Good luck.
