Hi Dan, I recommend choosing Bullet for your hydraulic roller camshaft. They never requested a core and after some research, they are known for quality cams. Find your grind specs (lift, duration and such) and contact them. My cam has five (5) same sized roller bearings and the roller bearings I use are made in the U.S. IMHO, steer away from any others that are not U.S. or German made. Cam roller bearings can be found on Amazon. Look for; INA HK5520 roller cam bearings. Cheers! Larry Sent using the mobile mail app