|The following may be your best starting point to visit the IBM System 370/390 jurassic park|
Hercules is an Open Source S/370-390 emulator for Linux and Windows environments. It enables the creation of a virtual mainframe system on your PC that must be dressed by installing an OS like MVS/SP or DOS/VS. You can find links to IBM documents and software too as MVS/SP is released under public license.
If you are interested in that world you can't miss this site and more the software is free.
I spent thirty years as system analist/programmer/manager around IBM mainframes and planned to setup Hercules, but other deals eated my time so never went ahead onto that lane after retired.