Are the rocker pedestals supposed to be an interference fit on the rocker shaft? I had to press them off the old shaft, and they don't slide on to the new one. Do I need to chill the shaft and heat the pedestals? Or do the pedestals need machining? What's the deal here?

They are not supposed to be interference fit. They are supposed to slide easily on and off.

If the engine has revved over 8000 or the pedestals overtorqued it can distort the shaft out of round. In this case use a new shaft and a torque wrench.

For extra high-RPM replace the spacing springs with solid spacers.

So the pedestals are out of round? I've got a new, nitrided thick wall shaft from Japan but the pedestals do not go on at all. Can I machine them and use them, or will they be unsafe? I'm building a 10,000 RPM motor that I will only rev to 8,000.

Do have a digital caliper? If so measure the brand new shafts and measure the pedestals. You will be able to tell if the are out of round and if they are different sizes. Double check and make sure the parts from Japan were meant to be used with the current parts. If you don't have a way to measure them go down to harbor freight and grab one, they are good enough to measure what you need.

Tom