Depending on your speed and rpm something even faster than 4.10 may be necessary.
My old K3500 with a 454 had 4.10 or 4.11 gears and TH400. It would cruise 75 mph pulling a trailer turning between 3200 and 3300.
Crusing that big motor that fast always annoyed me, but this was a factory setup and it worked pretty well.
And I absolutely agree on the brake upgrades!
