If you can produce a 3D block of the body style you want, then you are good to go. You can use the inner dimensions of the ULE body from its 3D CAD drawing to properly place and remove the solid parts as required. If you already have a 3D model of the ULE body created, convert the empty space inside to a solid model and use it to subtract from the new body block you have created. As long as you use a common reference point, everything will line up properly.
Except for the Automag in front, its usually the man behind the equipment that counts.