Rust in wheel well support

[NixVegaGT]

I noticed some pix of the later Monza's rear wheel wells. They look a bit different than my Vega:

http://www.cardomain.com/ride/2357894/4

I was wondering what you guys think. Should I fill in the gap above the unibody support? It looks like GM filled it in later... Let me know.

THanks guys!