Not sure if I understand correctly - are you saying cases are split, the bearing is out and you are trying to slide the main crank bearing onto the crank?
same thing with the output shaft bearing? the tranny I'm sure of will slide right in - it doesn't have to bear a load the way the crank does....
From my experience, there has always been some kind of interference fit when putting the crank back into the case half - I don't think I've ever seen it specified in a manual thought with a measurement.....guess you could mic the crank and take a bore gauge to the inner race of the bearing and see what the difference is.....interference is usually is thousandths - you can't rock the bearing can you? heck if you've got the motor all the way apart - spend the $25 and get a new bearing right?