2 Radios plugged into 1 Speaker?

So I will install a new radio in my glove box, but I would like to hook up my original solid state AM radio on dash speaker in my 71 Duster.
So hooking up two radio to one speaker is it doable?

Wanted to know if I can do this or not....the stock radio look cool...would be sweet to still have it hooked....but don't want to fry anything.