Do not confuse horsepower and torque.
You may be able to get circa 1985 360 horsepower out of your slanty, at some higher rpm. But you can never get 360 torque out of it unless you supercharge it.
And to tow 3000 pounds, with 3.21 gears, you are gonna need torque, cuz 65= about 2800rpm (10% slip) with 28"tall tires.
My guess is at 2800, it will take 150 footpounds..... or more. It's gonna take a lotta lotta throttle......