Here's the USDA Forest Service Brochure on the Longleaf Trail

The MS 50 is run on the two loops at the top of the map 
(It does not use the loop that goes by Tiger Creek church)
The start/finish is at the Longleaf Trail Camping Area (arrow)

Topographic Map

 Unfortunately this map does not show the trails, but it does show the contour lines. Note that the high and low elevations in this area are between 250' and 350', so those of us that have trouble with altitude are safe.