GR, could it be maybe 3681056 maybe? That is a 73 440 standard. My books go back to 74 but the 73 unit crosses up to the -----866 in 74.
Cuda Hack is right in that many, many things are usually changed/gone/modified, or destroyed on these. Its a shame but hey, these things can be over 50 years old!
When new, the 866 was built like this: it used a short accumulator spring under the piston, it had a 3.2 ratio KD servo lever, it had a controlled load KD servo with single outer spring, it had a plain governor spool valve, a purple coded valve body, a 4 pinion front and 3 pinion rear planet carrier, 9 springs in the front clutch retainer with 4 friction discs, and it had a standard input and output shaft (not specially heat treated). Forgot to add it has a heavy inner governor weight and a green spring in the governor.