How much improvement will I see?

Drag radials and the bias slicks are different animals when it comes to tire pressure. Seen way to many with DR pressures in 14-16 and suggest 20-22 area for a car like your.

People stuck in the 80's along with converters thoughts in many ways. Usually there is a bunch of 60' locked up in the front of the car.

If you haven't run it with the new converter, I'd put the squirter back to stock or next size up.

What is the engine combo? Altitude? Saw a video and it lays over really badly when you step into it.