Engine type identification

[drid]

I have just removed the motor from my father's old "hippy-van" and i am trying to find out what type it is.
It's not the original motor so i do not have any information but the following:
1) It has dual intake port
2) The case has the following markings:

28ME Mexico AS41
043 101 101 A
​

Any clues?
Thanks

 

[Topaz]

 

[Canamryder]