Fleetside Bed Sill Repair Suggestions

[adis]

I bought a decent '84 8' fleet bed locally to go on my '76 K20. The idea is to get it all put together as a work truck, so I'm not concerned about looks, only that it can handle a load and won't rust (much). I am a novice welder, and looking to use this as a way to practice, so forgive me if it seems ignorant. Everything on the bed is pretty good except that several (most) of the bed cross sills are rusted where the bed bolts go through.



I don't have the money to buy a whole new bed and I haven't seen anyone who makes replacement sills for the fleet. Do any of the aftermarket firms make a replacement bed cross sill for the fleet? If not, how is this type of repair usually accomplished? I was thinking of sectioning in pieces of sill from the old bed, or perhaps using 14 ga. 3"x1.5" steel pipe like this:



What I'm concerned about is the strength of this type of patch. If I section the piece by butt welding the ends to the old sill and spot weld it to the bed, will that be strong enough to hold a load at the seam? Will a repair like that hold with 1.5 tons in the bed? If I reinforce the butt welds will that do, or should I not section pieces and instead replace the entire length of the sill (which means grinding out a lot of spot welds...)

BTW, I'll be doing the repair with my Millermatic 140 mig using solid wire and gas, so I Should be able to get decent welds through the original sills which were 16 ga. Thanks for any suggestions or advice. - mark