There is an easier way, as you describe there is a lot of cutting and compound curve work cutting those major panels and then the extensive welding.
Start with these from a donor (reciprocating saw, junkyard cut, leaving extra meat):
https://www.flickr.com/photos/advance-design_parts_co/8129371322/in/album-72157631868452754/
Finished sides look like this and don't hit any structure or alignment issues.
https://www.flickr.com/photos/advance-design_parts_co/19284317059/in/album-72157631868452754/
https://www.flickr.com/photos/advance-design_parts_co/18849820823/in/album-72157631868452754/
I used to sell these on eBay from parts trucks, I can provide instructions and more pictures if interested parties email me. It is a lot of work Jim but I am sure it will be perfect when completed.