The tub your planning on replacing looks like it has a bunch of CF stuff already...not sure you'll get much benefit.
I'm also curious to ask if the tub has integrated diff housings or if they can be removed to add to your project.
If they can be swapped, then your best bet is once you have the material (www.dragonplate.com
is my favorite) you can just clamp the old tub to your sheet, mark/drill and mount the sheet so it doesn't move and then have at the cutting, grinding and shaping process.
I've also had good success with scanning a tub at full scale and then printing that on a decal sheet to give yourself a template to work around.
As for making tools, I've had good success with mounting a dremel router base attachment to a small table to make yourself a "router table". It has the option to remove the dremel from the base so you can hand grind if needed and gives anice flat area to hand manipulate the chassis template for consistent grinding.
Good luck with your endevour.