Improper ordering may result in parts failure. Watch for variations from stock radius in aftermarket lifters. Make sure sufficient oil volume reaches rockerarm end of pushrod to help prevent galling due to excessive heat generation. When possible, try to use larger diameter pushrods to spread out the load and lower the stress on the tube. This will help lesson pushrod deflection.
Many problems occur when a pushrod is inadequate for the application.
In high RPM applications tapered pushrods are a must for the serious racers. Increased lift at the valve will definitely be measurable. Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more then needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient.