I didn't get into measuring the frame, but I noticed that the distance between the front edge of the k-frame and the end of the frame rail is 1/4" less on the passenger side. I have no idea if they should be the same or not though.
Thats a good question. I'm not sure where you could look it up. I'll do some research and get back to you. I have some old body and frame measuring books I can look thru. Talk to you soon