Why is there a chevy dizzy in my 360?

That appears to be a MSD 8534 billet distributor for a Mopar SB.
It looks tall because like a Chevy, the advance mechanism is directly below the rotor and it uses a Chevy style tall cap, note the cap attachments. If you look closely, you'll see that the distributor body is shallow compared to a Mopar. I haven't measured, but I doubt that the over all height, when installed is much taller than a Mopar.