I've heard mixed information about the bench seat mounting hole locations. Some say they stayed the same from 68 to 79 while others say they changed between 72 & 73.
I do know for sure that the 73 - 79 ones are all the same. The holes are 45 1/4" apart (side to side) and 14 1/2" apart (front to back). Here's a pic of the floor in my 77 showing the bench seat mounting holes:
If the floor pan in your 69 measures the same then the 76 seat will bolt right in.