Another way of attaching a sidemount base to a rifle like yours, is to do like what is done in this picture
the holes that are then drilled into the receiver are well below
the ejection port. Of, course, one should mill a slot into
the base just in case you ever find a Petersen device to go with the rifle.
One thing that might be problematic with putting a sidemount base on your rifle is that they took the wood
up really high on the left hand side of the receiver. Some wood will have to
be removed for a sidemount base and there might not be enough remaining to retain structural integrity.
