Rear bed panel/channel...fix help please!

[Ochre]

Just got a bunch of parts in to patch up my beaten ole blazer!

Front cab support (OEM style) & bed panel section arrived yesterday, floor section is in the mail (supposedly).

Now, like most first gens, the rear of my bed has been eaten away by rust. It's gone thru the top "bed", eaten away the spacer between the bed and the channel, and eaten partway into the channel.

Now, it occurs to me that while I have some sheet steel and access to a brake, I want to fix this once, right, and not have to worry about it ever again (so after I get done, lots of POR-15 will be involved). So, being that the channel is eaten thru in a couple places (total maybe 15" of rustout, across the back sides) I was thinking I could spend hours and hours patching in some bent metal, and still worry about some thin sections, or I could replace the whole channel up to the extreme sides (which aren't rusted out) with fresh metal.

Being that I've got a discount metal shop nearby, I was curious of the dimensions and thickness of that rearmost bed channel so I can shop around and see what the cheapest place to get it from is. (I don't trust the thickness of my trucks panel since it's got some bad rust, and I don't want to cut into the not-rusty areas to measure x, y, z until I've got the new panels with me to compare)

Thanks! I'll be sure to post up lots of pics as work progresses on this thing.