Bent Frame???

Look at the four mounting points where the K member meets the chassis and see if those bushings look wasted and/or you may be able to pull each bolt individually to check to see if they are bent (I would caution that if they have never been out this may prove very difficult to do as you could break them, also if they ARE bent you may not be able to remove them by any means other than cutting the heads off and dropping the K frame). That is one possibility. The other would be to have another shop give you a second opinion. I am not saying anything bad or against the shop you had do it, but it is possible that they just don’t want to mess with it as they would have to do it for nothing since I would assume they warranty their work, and most shops I have dealt with will try to pass the buck to avoid that. Sounds to me like it isn't straight yet. Have you had it aligned or did the frame shop you had do the frame also do the alignment? Might be worth a trip to an alignment shop and see what they say, they should be able to tell if the alignment was set-up to account for the chassis not being as straight as it should be. It's always a pain to bring a uni-body back into spec after a hard hit.