Isn't this from an mid 60's rambler ?
I would say it's an M8 Model,
I have a M11 out of a '69 343 car
and the tag reads "W.G. DIV.AS8-11"
so it appears the last number after the dash is the Model.
Not sure in your case what "-8H" would be.
maybe Model 8 Heavy Duty ?
Have you seen this page ?
http://www.gremlinx.com/AMC-Transmissions.htm