Keith- Measuring from the bell center of a BB 727 to where the tube crosses the plane of the measuring tape, I'm getting..
11-3/4" to the inside of the tube.
12-3/4" to the outside of the tube.
The outside of the top of the tube looks to be 13-1/2".
Here is a picture that explains how these nubers were measured. The dipstick itself wont add more than an 1/8" to the outer measurement if the lock "handle" is positioned to the inside.




Here is a shot of how it mounts and where it sets.The mounting strap fit to the outside of the shield bracket. -Tom.