Glenn,
There is more information needed here. What type of riding do you do, where do you want the power, do you want it from crack of the throttle through mid range, do you want the power mid range to the top end?
Are you doing anything else to the bike, such as larger throttlebody, head work, open air cleaner, pipes.
What type of tuning tool are you going to use? SERT / Power Commander / Thundermax / Daytona Twin Tec ?
Are you wanting to stay chain drive, gear drive.
Some examples
Zippers 575 bolt in cam power from word go through the mid range
Freedom bolt in yb14 SE power kicks in around 3000 - 6000
SE 251 a little broader torque band doesn't ramp quite as quick as the Zippers
Similiarly you have the Woods 77 cam .... I haven't tried this one but one or 2 on the site have.
The Zippers and the Freedom both come in chain drive and gear drive the Harley SE 251 only comes in Chain.