Need to know the dimensions of the rear dovetail (series 70-80 Govt. 45 ACP).

Measured dimensions (caliper) from a "real" Series 70:

            0.348" wide across bottom of dovetail
            0.237" wide across top of dovetail, measured at top C/L of slide
            0.110" deep, from top C/L of slide to bottom of dovetail cut

These are the dovetail slot dimensions, not the sight.  Approximate only--worth what you paid for them.  Good luck.