1992 Dodge Dakota 518 overdrive transmission

bbrroowwnn said
Am I safe in assuming the A500 is the overdrive version of the 904 and the 518 is the overdrive version of the 727?

Yes

RedFish said
Yes except the 500 is closer to an overdrive version of the 998/999 as it has the same lower than 904 gear set.

Apparently not all A500's (or maybe none?) have the low gear set. I rebuilt a 1991 A500 and it did not have the low gear set.