Jerry,
My understanding is that there is that there is not much difference in the OAL of the various Spence 'original' cartridge cal. (You will find more variation in OAL within the various ammo makers that you will in the Arms makers.)
Case length, however can vary greatly between various round. The 56/56 case being the shortest case, 56/52 is slightly longer.
Both of these were designed by Spencer intended for use with heal base, outside lubed bullets.
The 56/50 was designed by Springfield and was meant to be an inside lubed bullet. These cartridge cases are the longest with a rather heavy and long crimp. (Spencer did not like this long crimp, so he developed the 56/52 for his 1865 models.)
Springfield also helped develop the 56/46 bottle neck cartridge with outside lubed bullet. (Springfield wanted to get away from the outside lubed bullets because the lube 'could' collect dust and dirt during combat that could cause damage to the bore.
The 56/46 bottle neck case can be made from the longer 56/50 cases.
I hope this info helps?
My best,
Blair