Hi Jan,
What you described sounds similar to what happened to my -6, the previous owner had an engine out just after take off, lots a damage after flipping over, I had a close look at the airframe, made a list of the parts needed to be replace, calculated the costs then made the decision that it was repairable, I've been working on it for almost 18 months, I could have finished sooner, I'm taking my time making sure everything is right before I put it back together.
I don't think it's necessary to replace all the AN bolts, have a detailed visual inspection of the bolts around the engine mounts, landing gear, wing attach points, any area that might have had higher than normal loads during the crash. If you see any ridges on the bolt shank, bent or damaged threads, replace the bolt.
Do you have any photo's..?? Is the airframe completely damaged..??
Good luck with it, if you do decide to rebuild, your going to have a great experience. I've got a blog showing what I started with and where my rebuild is at now.
http://rv-6rebuild.blogspot.com/
Cheers,