A 500 or a 518 will directly swap with each other without driveshaft swaps, etc. Same exact OD housing used on either one. Unlike a swap between a 904 and 727, these OD transmissions are the same overall length. I've put 518 (46RH) in place of 500 (42/44RH) a couple of times now. I'd go with the heavier duty trans of them every time.
But then I live 2 county's south of Chicago, among corrnfields, avoid Chicago like the plague anyway, and with all else being equal I'd rather row gears any time I can. Though I've been hurt badly twice over the years (right knee and then the ankle several years later) and both times the DR saying whether I could drive depended on whether my ride was auto or stick... Both times I had stick equipped vehicles so had to borrow vehicles or be chauffered around.
But yeah I have heard that Atlanta is 10x worse to drive around in than Chicago which is plenty bad in its own right. I'll have to take the word on the street about Atlanta, never been there.