How much gain with lower gears?

1st thing I do is take it to the track and dial it in as is. Then go from there. Easier to figure out from a starting point. Cause you will know your mph, peeps can figure out how much potential you have with your ET and figure out your optimal gear then decide if you want that or something in between or stick with what you got.

I got to do the same thing with my 2.96 geared magnum engine.

Plus the main benefit with 408 is you can run less gear than a 360. You running 3.23 is like a 360 running 3.73 and you running 3.73 is like a 360 running 4.30 etc..