I have a 1966 Fairlane GT with a 482 FE and a toploader. I am installing a Gear Vendors Overdrive which will not clear the transmission hump at the rear. I am going to need about 1" to an 1 1/2" to clear the hump. How much trouble am I asking for by changing the drive line angle with shims under the transmission cross member? The car has Calvert Bars and I should be able to shim the 9" axle to get the drive shaft angle correct. Should I just get it over with and cut the floor? This is a pristine no rust ever car.  This project has been dragging on for about four years and I am running out of oxygen.  This is a street car not a drag car (well, maybe occasionally), so I don't want a lot of drive line vibration. Give me the benefit of your experience and it's hard to hurt my feelings. I don't like doing things half a**.