I misread your question on headers. I thought you were getting rid of your inner fenders.
I have Doug's on my 66 Dart. It's a 360 4-speed setup. I have a lift in my garage so the headers were not that hard to install. I'd make a couple of shims for the motor mounts if you have to lift the engine a little to clear the torsion bars. I have Schumacker motor mounts and isolators on the car and they are a tight fit.
I used a rebuilt mid 1990's Dakota starter that I picked up at NAPA. No problems at all with it's installation.