Pace Arrow cab air conditioner compressor oil fill

Thanks for the comeback.
Bought the compressor from O'Reillys. The name on the box was Murray, mod# 58950. The only number on the unit itself was a small tag with
2370191. Also maybe you know how hard the clutch should be to turn. I can't turn it with bare hand. I might be able to turn it with a strap wrench??
I intend to replace the drier and vacuum the system down.
Thanks.........Hal