I’ve never done an 833 to a magnum, but I am right in the middle of doing a T56 magnum to a 5.9 magnum and it was very straight forward. From the searching Ive done it seems the 833 is a direct bolt on affair.
I have a A-833 4-speed on my 408 Magnum Stroker. I didn't need to do any crank modifications, just used the roller pilot bearing you mentioned. But, I seem to recall when talking to Brewers that they mentioned to check the crank to make sure it was drilled deep enough for the input shaft of the 4- speed.