Mild 340 8 3/4 gear and possibly converter question

I tend to err on the side of caution these days. If it is a street car with the occasional trip to the track I would run 3.55 gears. With your short tires it will be more like 3.73.
Even with taller tires it will pull fine and the converter will put it on the cam.
Remember it is a light car and will be plenty quick.