67 Barracuda Big Block K frame keep it or change it ??

I know this doesn't answer your questions, just an fyi.
I have Shumacher headers, fit great even with a 4 speed.
Manual KH brakes, rebuilt years ago, stops great, straight, no issues.
Manual steering, I just have to turn the wheel the opposite direction as the car is moving so I'm not breaking my arm or the wheel, for example when backing up out of a parking spot.