I am planning a Boshin War project and I think the French around 1870 are my best bet at proxies for the westernized units. As I basically know nothing about the 19th century military uniforms nor about the French during the Franco-Prussian war. Could someone help me explain the difference between the Imperial and the Republic infantry in tunic. From what I can see the difference is that the imperial have a slash for webbing and decorative pieces on their shoulders while the republican infantry have crossed webbing and no decorative pieces on their shoulders. Is that correct? 

Additionally, does someone have a close up picture from the Prussian Infantry? They might be suitable for infantry of the Satsuma domain, who used tall conical hats. 

The Republican infantry in tunic do not have the French greatcoat or the shoulder epaulettes. I kn ow absolutely nothing about the Boshin War, so do not know which would be the most useful French figure to use.  Is it in Japan? The Prussian 1870 infantry wear the spiked leather pickelhaub helmet.

Ah then the Republican infantry is more fitting. 

The Boshin war was an Civil War in Japan, 1868-69 between the Shogun and Pro-Shogun clans and Anti-Western/Pro-Imperial clans. 

Each clan had their own army and in various states of modernasation. There wasn't much uniformality in terms of gear and uniforms. It went from traditional to modern/Western. The republican infantry in tunics seem a good fit to represent Denshutai, French trained troops of the Shogun. 
For the moder traditional armed troops I plan on using Zouaves. Formed for western rifles and skirmish for the traditional matchlock guns. 

A suggestion for the conical hats: the relatively smoother-surfaced pith helmets on British colonial infantry might be better than spikey 1870 Prussian pickelhaubes.

Nice project. (Myself, I am more interested in the later Satsuma Rebellion, specifically because the battle of Tabaruzaka is big enough to merit a "Bloody Big Battles!" scenario some time.)