Correct, that is the factory radiator overflow bottle/tank. To provide better context, I attached the two "before" pictures, which show the factory Tacoma shroud and the Camry fans and shroud prior to modification. Basically on the Tacoma shroud I left the coolant tank section and the edge that touches the radiator untouched so it should bolt up and function just as stock. I removed the old fan ring and portions in the upper left and lower right to provide room for the new fans.
I was hoping just to be able to use the Camry fans in mostly their existing shroud without separating the two by mounting them diagonally, however it would have overhung the sides too much and caused interference issues.
Edit:
I added a few pictures of the assembly in progress. You can see my high tech work station (porch), custom aluminum workbench (step platform) and my ultra fancy plastic welder (40W soldering iron). The other pictures show a piece that I cut out before and after I heat welded it in. Note I just used the pieces I had to cut off the two shrouds to fill in the gaps that were left.
