fixing rust hole above wheel well

[chevy1]

Hey everyone, Im looking for any tips on filling in a rust hole above my wheel well on my box. Rust ate awat the edge so i have no guide if i bondo it. Rest of box is pretty good, just that one spot. Should i weld some sheet metal in first? Any help would be appreciated. thanx

[ccz145a]

The piece you need is here: http://store.73-87chevytrucks.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=7&Product_Code=0850-147-148T&Category_Code=7387Beds

[kcwis]

I also need a patch panel like this one but for the passenger side, I received one from another vendor but it says slip on panel,and seems to be very light gauge and the wheel well lip width does not match ,it's only 1/2 inch wide, oem is almost an inch. I tried the link but it doesn't go anywhere.other vendors also only offer the smaller lip style.