im swaping to a roller cam big block chevy from flat tappet hydro is there a standered size shorter push rod i need. im guessing the roller lifter will be somewhat taller  

If you're using stock heads that haven't been milled, or if the block hasn't been decked, then the pushrod length for converting to roller lifters is pretty standard. But it's always a good idea to use an adjustable length pushrod to verify proper length to save yourself any headaches.  

Thanks for the reply i guess ill have to get the push rod length checker cause i dont have the history on the engine