smooth rear of cab / cab corners rotten .......HELP!!!!

Im trying to find the best way to smooth out the rear of my cab because the cab corners are rotten and i dont wanna plate it all shabby looking. id rather make it clean. ive used the search button and still cant come up with info so now im asking the people. thanks!

sheetmetal??

Like This???

Theres plenty of ways to go about it...

IF it were me, I would end up taking, say an air hammer gun with a metal shear tip and cut the metal out where you want to remove it and then take a sheet of the metal and weld her in how you want.

Although, I would'nt do a smooth rear cab. I would just go to a wrecking yard and take an electric shear and cut out the cab corners and replace them..