Since I had my Late build 1977 dash out I have been toying with the idea of installing LED Bulbs...
Don't get me wrong, I have no issues with incandescent bulbs, the issue I have is with the 1950's style single wire socket used from the 50's through 1977...

I found an old tread from forum member Greg from 2018 where he used Side marker sockets to replace his single wire sockets as shown above...
Greg stayed with incandescent 194 style bulbs...
One of the changes made to a late 1977 main dash harness was a Shift indicator light socket was installed no matter if the car had a manual transmission or automatic transmission...
The socket diameter is 5/8" same as the Speedo/Tach socket diameter...
I did purchase a side marker socket like Greg used but I really didn't feel comfortable with the way if fit not secure for my liking...
So a little research I found the same socket that was used for the shift indicator light on my late 77 was still available and had a more modern T-10 wedge base socket for a GE 194 bulb...
Now for the crimp terminals, I used 2 different terminals...One has wider wings used for the double wire and one with closer wings for a single wire...
I'm using GLX 18 gauge wire, same colors as the existing wire colors...Original wire size is 20 gauge wire
You may see on the ground bridge between Speedo & Tach is a 2 cell housing, I will use this housing and run 2 new ground wires to the Left Hinge Pillar area...
My Headlight switch is from a 78 and newer switch so it has and additional ground lug not found on a 77 switch so I took advantage of that ground also....
I will use the 6 cell & 8 cell connector housings to connect to the main dash harness...Male side to Speedo/Tach assembly's F/M to the main dash harness...
Here is my build...