That could make sense. Sounds like what Atlas did is made the left leg the same basic size as under the larger machines so that the right leg didn't have to be changed. But modified the top rear of the left leg to fit the 6" countershaft bracket. M6-800 was the model number assigned to the 6" floor stand.
So it would make sense that the left leg was M6-801. And the right one is 10-441. The top board for the larger machines was 10-442-nn, where "nn" was the bed length. So the top board, if it's still original, is probably M6-442-36.
The motor base might be S7-108A of M6-22A or ?. The motors are all about the same physical size but the motor bases all seem to have been attached to the countershaft brackets. Which varied quite a bit.
Unfortunately, unlike the 10", none of the Atlas or Craftsman 6" parts lists ever seem to have included the motor base. Possibly because all of the manuals that actually show how to mount the lathe show it on a bench with the countershaft bracket and the motor attached to the bench top. The motor base probably only came with the floor stand, which was an extra cost option.