I have here an old Ruger 44 carbine.

The chart says #47 rear and #68 front.
The hole spacings are right, but the radius and height of the #68 is wrong.

The receiver is a constant 2.750" diamter, but the #68 mount is a much smaller radius and too high to match the #47.

I think I am going to have to mill a radius on the bottom of my #68 or buy another #47 and drill in it a third hole.