The modified Mustang bridge is great. So is the Jazzmaster Mastery Bridge.
The greatest effect either will have on the sound of the guitar would be the fact that they intonate better 😆 .
To fill the old vibrato cavity, simply carve a block of wood to fit where the old bridge was. At that point you can glue it in and finish over it, I guess, or refinish the guitar.
I'd suggest getting the block made out of a different type of wood than the body. Perhaps mahogany, for a slightly warmer, vibe-yer vintage tone.
-Cy
