Pushrod for hydraulic cam and 273 rocker arms
Here are a few good related threads for reference:
Here's some good info in this thread on using the 273 rocker arm and adjustable nuts:
273 adj rocker stud and lock nut?? Where?
Here's a thread with all the info for push rods using 273 adjustable rocker arms with a hydraulic cam:
273 stock push rod length?