273 Rocker Arm to Shaft Clearance

There is no need to go to chrome shafts because the factory shafts are hard steel.
These engines lasted for years with factory shafts, zero problems. Thermal expansion is not a problem @ 0.003" clearance with both parts expanding together & both have the same expansion rate.
The most important thing has not been mentioned. Which is NOT to over torque the shaft mounting bolts which could deform the shafts & cause the rockers to bind.