cool man, yeah I'd double check the measurements and go from there, and you're right, if the dimensions are off, not much you can do if for some reason the K-Member is out of spec. Ma' Mopar was a bit sloppy with the metal work back in the day, and it is possible to have one out of speck from the factory.
Of course I don't know the history, but I assume you have new motor/trans mounts in, and if not that'd be the next place I would consider replacing.
I fought long tube headers for about 2 months, gave up and found out 2 years later how badly my K-Frame was messed up from a wreck.
