I have a 292 that was rebuild by previous own about 15k ago runs great but I would like to put a cam in it more for the sound at cruise night than a lot of power (I don't try and race it). It has a E intake with a holley 4160 carb 390cfm FOM and duel exhaust, but no headers.  I have been looking at 2 cams that mummert has.  A y265s and a y270s which is ok with a fom but also calls for headers.  My ? is whats the downside of using the y270 with out the headers? also the cam bearings and lifters were new 15k ago, Do I need to also replace them?