I can't provide drawings, but tbh I'm not sure they will be of much help. You'll have to line it all up as you go.
Depending on what you are doing exactly, you'll need to remove the rear cross member from the RRC and fit a Defender one, the rear legs are arched on a RRC, so you'll probably need the body tub to balance on the new cross member while you line it up.
You'll also need to add the body out riggers front and rear.
Are you looking to chop the wheel base down too, or try and make a 100" Defender? If the latter, then obviously the rear tub will need modifying somehow.