I'll let machine shop tom anwser your question about machine work that has to be done he is much more exp. then me at it.
and yes it WILL be a 383 bore and stroke change the CI not rod length.
As for performnce I know that everyone used to use 400 rods but have since switched to 5.7 I would think with the shorter rods you will have more side loading. Just like the diff. between 5.7 and 6 the 400 rods might cause or side loading and slightly more wear but guys did this for years and years so...