The typical Marlin 39A does not have a scope. They are drilled and tapped that one can be added.
Yes the receiver is grooved for scope mounts
Yes.Most marlin model 336 rifles have been drilled and tapped for a scope mount on top of the reciever.
about $140 depending on the condition
I would value your marlin rifle at between 300-350 dollars,which does not include the value of the scope.
Marlin did not make scopes. They had their name put on scopes made by someone else.
Contact Marlin
50-400 usd
$500 for a good one with a scope
no it has a 3/8 dovetail rail
About 250 without scope.
i have an older marlin 30-30 lever and i put rails and rings on it and they work great. hope this helps