Miscellaneous questions to which I can't find answers....

The tool you asked about can be found here
https://millerspecialtools.spx.com/Detail.aspx?id=766
It's not needed as I have done many many pushrods without it, but it's a nightmare your first time. It's used to hold the intake pushrods in place to align them for installing the rocker shaft. When removing the rocker shaft it's not needed.

The website above carries all the "special tools" found in the service manual. Just search the number under the pic of the tool from the manual.