.025 isn't a hole lot of difference, and bigger is better since the crank or flywheel doesn't actually turn the transmission...the clutch disc does that when the pressure plate clamps down against the disc. will the input shaft from the transmission fit through the 383 flywheel? it should, they are the same transmissions. I wouldn't worry about it.

you do have the pilot bushing in the crank, right? and this is a 440 crank that's been drilled for a manual trans (again, with the pilot bushing/bearing installed)?