Sliding door lock assembly

Hello,

It's tough to be sure without seeing the original handle set but your mortise lock resembles the 82-218 depending on how the dimensions below match up to yours. This lock is commonly used with the 82-030, which has 3-15/16" installation hole spacing and an adjustable thumb latch. Take a look to see if the specifications of these parts would work for your application. Thank you! 

Profile view of 82-218

Opposite side view 82-218

Hole center dimensions for 82-030

Dimensions for 82-030