When was 呌 replaced with 叫? I've seen a lot of books published near the end of the Qing dynasty where 叫 is usually always written 呌.

It does seem less common during the Republic of China era, but I'm not sure.

When was 呌 replaced with 叫?
You need to know about First Set of Variant Characters To Be Standardized:


  In October of 1955 the Ministry of Education and the Committee for the Reform held two important conferences in Beijing, the National Conference on Script Reform (Quanguo Wenzi Gaige Huiyi) and the Symposium on the Standardization of Modern Chinese (Xiandai Hanyu Guifanhua Xueshu Huiyi) , the first focusing on Chinese character simplification and second on the definition of Putonghua. The first meeting resulted in the passing of the Revised Draft of the Scheme for the Simplification of Chinese characters (Hanzi Jianhua Fang’an Xiuzheng Cao’an) as well as the Draft of the List of the First Set of Variant Characters to be Standardized (Di Yi Pi Yitzi Zhengli Biao Cao’an), both of which were given full propaganda support by the CCP, the government, the People’s Daily, etc. 


The original looked something like this:


  


In Chinese it is now called 第一批异体字整理表 and is explained like this:


  《第一批异体字整理表》，是1955年中华人民共和国文化部和中国文字改革委员会发布的正体字选字表，原来有810组，淘汰异体字1,055个（但“妳”、“粇”二字分别出现两次），于1956年2月1日开始实施。


The list contains:


  


There you have it:


  叫［呌］


These regulations seem to have come into place on February 1st of 1956.