Thanks, Ray. The stab width is a start, and will help me. I think for the tail fin, measuring along the top of the boom, from the panel gap just in front of the 42 degree gearbox vents, horizontally to the rear of the fin would be close enough. I've tried scaling up measurements from 1/48, 1/35, and 1/24 models and comparing them, and I got that the 'C' had about 6in. more chord, but needed confirmation. I think the chord of the tail fin is also 6in. more on the 'C' but, that still needs verification.
Agree on the inacurracies of stated measurements. They go all over the place. Some of the confusion may result from the various measurements as you showed in the dash-10. There are 4 different ways to measure the length. The authors you mentioned quoted one or the other, depending on their preferences. A.J. Pelletier, in "Bell Aircraft since 1935" even quotes different lengths and HEIGHTS between the 'B' and 'C'.
What I would like to know is, is the 'C' chord 6 inches greater than the 'B' chord, and how was that increase achieved... move the leading edge of the fin forward?, move the trailing edge back?.. or a little of both?