Advice on navigating header clearance issues.

I have a 73 dart swinger with a 318 and got some new long tube headers. The one on the passenger side only has clearance issues with the torsion bar but the drivers side is a bear... I can't install the steering box from under or over and the lower bolt won't even go in. Based on my research, I should heat up the header and dent them for these clearances. I guess I have two questions, is the a smaller steering box that would be compatible? And do I heat up the header mounted to the car to gage on how much it needs to be dented or do it off the car. How have other people navigated this issue?