I'm no A body expert but it wouldn't surprise me at all to find that the sheetmetal location is different between various years and models.

TTI has the engine location on their website. They'll tell you where the center of the crank should be side to side and up and down. Best thing you can do is put the engine where TTI wants it and then just deal with any problems that pop up.

I've sold the 2 1/8 headers and I'm switching to 1 3/4 headers. The 2 1/8 headers physically fit on my car but they required a very time intensive process of installing and removing. For example, it required a couple of days of work to change the starter.

On my car given my tools the only way to remove or install the headers was to remove the K frame. So the car had to go up in the air and then the suspension and steering had to be pulled away so the K frame could be removed. Once the K frame was off the car then the headers went in and out with 5 minutes of work. TTI says the headers can be removed or installed from below if the car is on a two post lift. I don't have a two post lift so I had to pull the K frame. I came to the conclusion that I didn't need the big headers for what I was doing with the car.