Slant 6 & A833

No, the input shaft should be the same diameter. Maybe what you're referring to is when people put a manual transmission behind a cast crankshaft not drilled for one. In that instance, you normally have to trim about 3/4" off the end of the input shaft, but to my knowledge, you don't have to turn anything down. The 833 was a transmission option for the early A with a slant 6, although somewhat rare.