I purchased a a 68/69 rifle with a German crown and am fireforming .43 mauser to fit. The length from top of rim to top of shoulder is 1.683 and the neck length 0.687. Overall cast measures 2.48. Dia. at base 0.537 and just below shoulder 0.524. I can't seem to find cartridge data that fits. Any ideas?

One at a time!  I'm trying to figure out how this all works.  Be patient please.

Number 3!

Ok, if this thing has not been rebored and rifled or alter in some form it should be a 43 Spanish. The 43 Spanish does come in different flavours/sizes and not sure why. I thought the 43 Spanish was a lightly tapered case and not a full blown bottleneck.  What does the bore slug at? 
Mike

I almost forgot, this is a really nice Peabody by the look of these pictures. If you can take a picture showing the top of the breech block, I'm guessing that the trough is full length and not a short one like in the Swiss rimfire or the 50 ca rimfires.
There is a Remington cartridge that is the same as the 43 Spanish but Remington called it a 44 something, maybe the 44-70. 
43 Mauser is different then 43 Spanish I think.
Mike

I slugged it but because it has 3 grooves it's kinda hard to be accurate. The best I can tell it measures 0.439. According to my research the stamp on top of the receiver and barrel is a German armory stamp. Supposedly confiscated from the French "like new, unfired" in 1870/1871.

That's a nice old Peabody.  Phil Sharpe (The Rifle in America) wrote that the Providence Tool Co. sold 39,000 side hammer Peabody rifles in 11 mm Spanish caliber to the French government in 1869/1870.  I think you have a survivor.

George Hoyem, writing in Vol. 2 of "The History and Development of Small Arms Ammunition" reported that the Spanish had accuracy problems with the 11 mm Spanish cartridges in their Remington Rolling Block rifles.  Presumably, your Peabody is chambered and rifled to something like the early Remington specs.

The Spanish attributed some of the problems to the bullet not completely filling the bore.  But the same cartridge seemed to work just fine for Argentina.  I should think that with the slow twist, a shorter, fatter bullet might do better.   You might think about paper patching some unlubed .44 Special or .44 Magnum bullets.

Do you have a copy of the Hull book?  If not I can describe the markings on the possible military models for you.