8395 appears to be a former Wiregrass Central locomotive that served in neighboring Alabama. Both 8395 and 4537 are rebuilds from EMD GP-7 or GP-9 models (lowered short hoods, new electricals and air filters), making them 50+ years old. These rebuilds (most work done in Paducah, Kentucky) were once commonplace on railroad in the southern USA. Now they are a vanishing breed, even on shortline railroads. 8795 is an unusual find for Georgia. It is an EMD SD-40T2, a "tunnel motor" unit once owned either by either the Denver & Rio Grande or the Southern Pacific before both lines were absorbed by the Union Pacific. This unit still retains most of the UP livery. They were called "tunnel motors" due to the low intakes along the rear of the long hood. Ostensibly, these units were better suited for the long tunnels in the mountainous west and able to draw cooler air with the low intakes. I'm not sure how well this worked in practice.
Very interesting finds!