The numerics appear at first glance to be a shared key cryptogram. Simple letter shifts were common in the Civil War era but easily broken. The fact that there are a number of references greater than 26 indicate a shared key or cross matrix cryptogram. eg. the number of the word from a shared page in a book (the bible often used as they were almost always KJV and readily available). The sender and receiver would know which page to use and viola nearly an unbreakable system. The problem of course is that 2 people have to know the key(which book,what page etc), break one of them by whatever means you have and you know the code.

Cross matrix is a rotating matrix of letters (rarely words) that does not need a shared key only a knowledge of method and where to start building the matrix, often times given in the first number or two (for example 144 could be a description of a 12x12 matrix with the start at the second number. If even rotate horizantally, odd vertically etc.) Tougher to use because the encoder has to take the time to develop their matrix, encode what's needed and the hope that the receiver can figure out what they have done. Weakest link again, the individual's capacity to keep their mouth shut under duress.

Any idea who Uncle Snort was? Maybe if you found out where and what he did at about the same time you could get an idea on your "code"? It appears to me to be a word code not letters as there is no indication, at least in your post, of word breaks and the number of numerics fit likely word match vs letter match.

John R