Check with the cam grinder first to see if he ground the cam with a 4 degree advance. Most of them do put some kind of advance into the cam when they grind them. If you use a '71 sprocket/chain kit and the cam is ground 4 advanced, you should be good to go. To do the job right, mount a degree wheel on the crank and use a dial indicator to degree the cam in on the specs provided by the cam grinder. Advancing the cam in relation to the crank will increase low-end power, retarding it will aid you at the top end.