The Clapp model is left more of a flattop and has more "meat" to dovetail into. Notice also the front sight is also raised.
I believe you would be best served to sell your gun and buy the Clapp if a Novak is what you want.
I believe the front sight height on the fixed sight regular GP models is 0.185". As a comparison I think the SP101 models have a 0.155". I would look through the online Novak catalog ( Novak Designs Inc. - Products ) and see if you can find a model of the correct height. If you are cutting the dovetail anyhow it does not need a Ruger sight per se but a sight of the correct height. If it is a rear sight you want to install I imagine you could cut the dovetail and do any necessary milling of a flat pad to go underneath the sight. You will need a taller front sight to go with it.