this on an 85 D150, 8' bed.
I want to do a complete total paint job on this truck. I have some bodywork to do 1st. Minimal rust, especially for a NW Indiana truck all its life. More body work because the old coot of a PO, couldn't pull in or out of a barn without scalping the door jambs, than because of rust.

There is a little rust at the wheel lips, I could certainly buy the repair patch panels, and splice them in/ and finish straightening the cave ins on both sides and call it good.

But, (1) I've done the wheel well patch a few times and can get it looking GOOD and stays that way for only a couple years. not long enough duration for amount of work involved. Every time after 2 years you see the line popping thru the welded seam between original and new metal. Right thru the paint. My son has that on his 99 and he bought it "freshly redone". Looks as bad or worse than it originally did with the rusty wheel wells. I have my thoughts on that. Hmm. I've never see that on a fully welded panel ground such that there is no visible remnants of the weld. I did use some elcheapo patch panels once and rust started coming through the paint and, yes, that did leave a line. But it was IMHO due to poor quality panels rather than the welding itself.

and (2) I have a pair of rust free, straight, complete bedsides here, whoever salvaged them cut the front wall of the bed, down the length of the bed floor all the way, just inboard of the wheel wells. Original metal from "back in the day". Like I had said, I have my thoughts on what causes welded in patch panels not to last. One of those thoughts is that the replacement metal used in the patch panels is somewhat incompatible, with the original parent material. some kind of reaction between original metal, MIG wire, and the pig metal from overseas that most patch panel material is made from. I have seen many, and done a few myself, trucks around here that have had that area cut out and repaired, (my originals, really AREN'T that bad, rust wise)

Anyways, I have the full bedsides. Went down to Georgia earlier this year, myself/ and hauled them back. It may be overkill/more work than I may "need" to do to make this right, but my plan is to, this winter, pull the bed and set it onto sawhorses in the garage. Then, Drill all the spot welds out of my original bedsides, do the same on the rust free bedsides, and plug weld the Southern bedsides to my original truck bed. No new seams around wheel wells to rust, replacing with original metal, rewelded at original attachment points/ Better, longer lasting repair, right?
I am NOT gonna cut my new bed side panels into "patch panels", I want to use them "whole", or not at all. For what these bedsides cost me, vs the price of patch panels, it was a no brainer. and I figure I'll have less shrinkage and distortion to fight, vs patch panels.

Anyways, now that that is outta the way here goes..... I believe the Georgia bedsides may be off of an '88. I know there will be a gazillion spot welds to drill out. I'm up for it. The question comes in, what are the chances that the drilled out spot weld holes will match up, between the 2 truck beds? If they do it probably would be pure coincidence. I'm not sure when Mopar went to fully automated lines but the newest vehicle I worked on ('74 Dart) none of the spot welds on the quarters matched. I had planned to buy a pile of Cleco's to hold the "new" bedsides to the old inner bedsides, and remove them/ as I fill in, and weld up the spot weld holes?

Next question; my 85 has the chrome trim at the top bodyline, and the 3-ish" wide, black n chrome trim at the bottom bodyline/ the length of the truck. My 85 is a 2 tone, white and maroon. Replacement bedsides are 1 solid color, (don't care, whole truck will be repainted after bodywork is complete anyway,) and the truck that the Georgia bedsides came from, didn't have the wide trim at the lower body line. I've seen vehicles that have had the trim clips simply sheet metal screwed onto a panel before, really don't want to do that. The trucks that had it from the factory, had some "rivets"/nails that the clips slid onto and lock into place. What is the "right way" to attach these plastic trim clips to something that never had them? If you have, or have access to, a stud gun (Unit-Spotter), they can weld the studs on for trim cilps.

What I am getting at here, is that on my truck, the 2 tone color change happens beneath the trim. I am not sure that I want to retain the trim/ because to me, that wide trim, [having nothing to do with how it makes the truck look (or not)], is nothing but a big "water trap," holding moisture against the body panels beneath them, and opening me up to increased chances of rusting out down the road. I do like the way the 2 tone looks, and will probably duplicate that with the new paint job.
If I don't hide the color transition under that trim, what's a good way to do that color transition without the "benefit" of said trim? Make sense? Put a piece of pinstriping over the junction of the two colors. AMC did that a lot.