I have no experience with either cam you mention, but I'm going to assume the "254" and "264" are advertised duration. Another specification or two I'd be interested in seeing are total valve lift, and something called "lobe centerline". Duration, lift, and centerline are all important to know when figuring where a cam starts producing usable power and how much low-end performance has to be sacrificed to get a gain at the top end. "There's no free lunch" is a phrase that definitely applies here. To take advantage of a higher lift and longer duration cam, compression must be increased, carburetion gets bigger, valves and ports must be enlarged, exhaust restriction needs to be reduced, and all of it has to work together. Once all that is done, low end performance will be much less than what a stock engine has. You will give away low speed torque to gain horsepower at high RPM.
Pay your money and take your choice, but in my opinion, the 254 cam would be as far as I'd go for a street-driven engine, considering the other specifications you've noted.
Jerry
