300winman,
I believe the taurus folks will tell you you can use scope / base on the 6.5" RB. I recently purchased base for 8 3/8" RB, saw ref. to mounts on 6.5".
The base is nice. I have mounted and recently put a bushnell red dot sight on it. Have app. 300 target rounds (lead) through it as well as app. 150 mid to "upper end" loads as well. Scope is rock solid.
So far with 240 swc lead and clays / hp38 I am getting app. 1.5" groups @ 25 yds.
With 210 speer gold dot and a stiff load of Lil Gun I am getting app. 1.25" groups. 5o yard groups are app. double. The WW 296 is slightly more accurate but the fireball is tremendous and alarms people @ the range. The w296 also has a much more pronounced "snap" in recoil (still a pussycat).
The verdict is not out yet on the red dot. I might try a 2x weaver next year.