This is the original Thing movie based on a story called, "Who Goes There" a science fiction novella by John W. Campbell, Jr., written under the pen name Don A. Stuart. It was first published in the August 1938 Astounding Science-Fiction. Wikipedia
I saw the movie on TV and was so freaked out, I had to go eat two bags of popcorn to calm down and sleep at night with covers over my face every time I heard footsteps.
In the older movies more was left to the imagination and I'll tell you that is much scarier than all the blood and gore they toss at you these days.