valvetrain is the main part of the motor as why they come with limiters.... rpms are almost always determined by the valve train beef it all up maybe go roller.. but beef it up heavier springs and light weight valves.. and for the push rods dont go lighter smaller... go bigger heavier sense that is were most of the stress is but on the valve train..i just read cant remember where but on race applications they were using much thicker push rods than stock much much larger... once the valvetrain is built i meant BUILT then i would start on the bottom end with steel crank.. and i really dont see the need for forged internals if you dont plan boosting or hitting it with nitrous... just high quality alluminum alloy pistons and rods.. the lighter the better remember when it comes to rpms... exception (pushrods) and good flowing heads with just a pocket port polish will do wonders for a well built valvetrain and member a better built valve train your allowed to run i higher lift and rpm cam 
