I bought a magnetic one that stuck to the bottom of the oil pan and the wiring was routed to come out the front.
I just plugged it in for the night.
When not using it, the plug was just pushed behind the grill and you couldn't see it at all. The magnet was very strong. Had no problems with that aspect.
Sorry, I don't remember the make/model. Pretty sure you could Google it and have choices.
End result was claimed to keep the oil 30 deg. F. above outside temp. I found the truck (hemi 5.7) cranked faster and started easier on really cold nights. I was in Sussex County, NJ, about 20 miles fron NY State and 30 miles from PA state line.
We had one really cold snap for about 3 weeks where it never got above 0 deg. F and had no problems .
Good luck.