Magnum yes...never heard it called the magnum hemi....as that would just be wrong.
The magnum hemi was a 5.7 engine, not 5.9, and it was a true hemi engine unlike the 360 cid engine.
It was a strong engine, but as has been said, thirsty. I had a 360 I built in the truck in my avatar (non-magnum version), and while it never got great mileage, it also didn't get terrible mileage either....in that truck with 40" tires and only 4.56 gears since that was the biggest that fit in the 9 1/4 rear at the time, I'd still get 8-9 mpg, and it also had enough umph to push that 6000 lb barn sized truck to a 9 sec 1/8 mile, chirping the tires on the 1-2 as it did it.