Downloading a tune from a standalone pcm

[Tater85]

I am getting ready to do some tuning and wondered if it was possible to down load a tune from a pcm sitting on a shelf? I have access to a zzp reprogrammed unit out of a buick regal. I am hoping it may be possible if I was to use an obd port from a vehicle and connect the necessary wires to the pcm.

Mostly for the interest of comparing stock tune versus what tune has changed.

What software should I buy for standard tuning without need for external data logging?

[TheMechanic]

Yes. Just need to create or purchase a standalone connector. They don't cost a lot and are easy to make.
Software wise if all your doing is comparing tunes just download HP tuners. It's free until you need to program. Any software will require some form of dongle/communication device to work. If you want to use HP tuners you will need their tool.
https://www.hptuners.com/mpvi3/