Can I use 26 1 3/8 tire to replace a 27 1 1/4?
No.  Bicycle tire sizes are a dogs breakfast of standards. The only standard that is consistent is ISO. 

According to Sheldon Brown, 27" is ISO630 and 26"  (the common sized MTB tire) is ISO 559.  

ISO630 (27x1/14) are available with a search on the internet e.g. Sheldon Brown / Harris Cyclery (not a recommendation)