Whats the difference in a 2015-2020 9.75 w/3.55 ratio? will a 15 fit in a 16? Electronic locker?

 

Are you sure it's a 9.75? If I recall correctly, 9.75 was only available as a 3.73 option

 

My 2016 has a 9.75" with 3.55 ratio.

 

yep both my 15 and 16 both have 3E55 9.75 on tag on rear diff. L9 code I believe?
Question is did they change the diff in any way to keep me from using a 2015,16,17,18,19,20 swap? Plug ends different? Track width?

 

Only things that might differ are whether they both have the locker or not and it sounds like you found matching so it's a straight swap.