My first thought, too. But cars didn't use "A" as a year code in the VIN, per the info I have found, which makes me think it was a truck or van which did use "A".
One theory would be that Dodge built a bunch of E58 motors in 1979 and then they didn't sell. So this motor sat around for awhile until it was either dropped as is into a rig sold with a 360 (assuming they had a 44bbl option), or converted to a 2bbl intake and used that way. It would explain the 6+ months that the motor must have sat to have early '79 casting dates and parts but marked as an '80 motor.
Really not a big deal, motor is pretty rough either way and if it needs to be rebuilt there really isn't any difference between a low performance 360 or HP one. Just has me curious.
