I'm not entirely sure, but I believe that the lens for the screen is different, as well as the direction of the End, BB, Escape, and Call buttons, I think they have slightly different shapes...
I have read that people have done swaps but I think its mostly the 8330 home keys into a 8310-20. most do the home key swap to get the black keys.
like you said the info is a bit sparse but I havent seen anyone post that they have done it... just people saying they think it can be done. my guess is it might work with a complete housing but there is a chance the mother board wont fit right as the two phones have different capabilities/features... gps, wifi, memory ect..