rogpatt,
It isn't a normal procedure to add a nut when the fastener is threaded through a piece. The SOP would be to include a lockwasher, or some type of locking compound the the bolt or screw.
It sounds like you are nervous about this. Not every situation calls for a lockwasher, although the flexplate to converter connections I can think of did use them.
If this is going to bug you, and there is ANY access to the area, you could put a drop of 'post assembly' Loctite on the threaded protrusion of the bolt.
Stuart
