How to ID a real MP 360 crate magnum, id the HP rating, and what's it worth?

If it’s a real one there will be a part number on the crate. May also be a yellow sticker on the block with part number.

All 380 Magnum crate engines from Mopar had an M1 single plane intake.
All lower power (300 I think) Magnum crate engines from Mopar had an M1 dual plane intake.

It’s worth whatever someone is willing to pay.